LED lighting device

ABSTRACT

A light emitting diode (LED) lighting device includes a circuit for receiving an input power from a power source and outputting a rectified power, an LED unit including a plurality of LED channels connected in series, each LED channel having a front end and a rear end, a current sensing resistor, and a switch circuit unit. The switch circuit unit includes a plurality of switches, and an N th  switch is connected to the rear end of an N th  LED channel so as to control an operation of the nth LED channel, and is controlled by a sum of a current of the N th  switch and a current of an (N+1) th  switch, which flows through the current sensing resistor. Forward voltages of the LED channels are unevenly redistributed so as to keep power consumption between the N th  switch and the (N+1) th  switch substantially same, and N is a positive integer.

CROSS-REFERENCE TO RELATED PATENT APPLICATION(S)

This application is a Continuation of U.S. application Ser. No.14/765,610, filed on Aug. 4, 2015, which is the National Entry of theInternational Application No. PCT/KR2014/000998, filed Feb. 5, 2014,claiming priority to Korean Patent Application Nos., 10-2013-0012835,filed Feb. 5, 2013; 10-2013-0056432, filed May 20, 2013;10-2013-0056433, filed May 20, 2013; 10-2013-0056435, filed May 20,2013; 10-2013-0056436, filed May 20, 2013; 10-2013-0056437, filed May20, 2013; 10-2013-0084812, filed Jul. 18, 2013; 10-2013-0084813, filedJul. 18, 2013; 10-2013-0084814, filed Jul. 18, 2013; 10-2013-0084815,filed Jul. 18, 2013; 10-2013-0084816, filed Jul. 18, 2013; and10-2013-0099825, filed Aug. 22, 2013, the entire contents of which areincorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention is related to an LED (Light Emitting Diode)lighting device. In particular, the present invention is related to anLED lighting device in which a switch operating an LED is automaticallyconverted by an input voltage and the heat generation on a switching IC,when a voltage equal to or greater than a rated voltage is inputted, canbe prevented.

BACKGROUND ART

An LED diode (hereinafter, it is referred to “LED”) is used in lightingdevices to satisfy requirements of low power consumption, highefficiency, and long lifetime.

In order to use an LED as a light source, a switching circuit to operatethe LED according to an input voltage is necessary.

A conventional switching circuit includes a voltage sensing circuit orperiod sensing circuit to sense the amount of a voltage or an inputperiod of a voltage, thereby controlling a switch corresponding to anLED. Since the conventional switching circuit includes the voltagesensing circuit or the period sensing circuit, its entire size is toobig. Thus, the marginal area to include more LEDs is reduced.

In addition, the switching circuit is formed by a FET, and the FET IC isa sensitive component, and very weak to heat. Herein, when an inputvoltage equal to or greater than a rated voltage is inputted, asignificant amount of heat may generate at the switching circuit. Thatis, when the input voltage equal to or equal to or greater than therated voltage is inputted, current with high amperes flows through theswitching circuit, thereby generating a significant amount of heat atthe switching circuit.

In U.S. Pat. No. 6,989,807, in an AC (alternating current) input voltagehaving real time voltage change, LEDs are operated under the real timevoltage change condition by controlling a plurality of switchesconnected in parallel to a plurality of the LEDs connected in series.However, since a voltage sensing circuit sensing the input voltage isincluded in U.S. Pat. No. 6,989,807, an area for mounting more LEDsdecreases, and a significant amount of heat generates at the switchingcircuit when a voltage equal to or greater than the rated voltage isinputted, thereby increasing power consumption, reducing its efficiency,and increasing occurrence of malfunctions of the circuit due to thesignificant amount of heat generated at the switching circuit.

DETAILED DESCRIPTION OF THE INVENTION Technical Problem

The present invention has an objective to decrease the heat generationat a switch unit and protect the switch unit by generating heat at aresistor to distribute the heat generation when a voltage equal to orgreater than the rated voltage is inputted to an LED unit in which aplurality of LEDs are connected.

The present invention has an objective to form a switch unit without anyinput voltage sensing circuit or any input period sensing circuitsensing an input voltage, thereby adding additional LEDs can be added ina restricted area.

The present invention has an objective to prevent a flicker phenomenonby connecting a capacitor to an LED.

The present invention has an objective to economically control dimmingof LEDs.

Other objectives of the present invention can be easily understood bythe description of following embodiments.

Technical Solution

According to an aspect of the present invention, an LED lighting device,including: a power source unit supplying an input power; a rectificationcircuit unit for receiving input power from the power source unit andoutputting a rectified power; an LED unit having a plurality of LEDchannels connected in series and a resistor unit connected to the lastend of the LED channels; a current sensing resistor; and a switchcircuit unit including a plurality of switches, wherein an n^(th) switchis connected to the rear end of an n^(th) LED channel so as to controlan operation of the LED channel, and is controlled by a sum of a currentof the n^(th) switch and a current of an (n+1)^(th) switch, which flowsthrough the current sensing resistor.

Herein, a resistor unit may be connected to the last LED channel, theswitch circuit unit may include a switch connected to the resistor unit,and then the resistor unit may distribute and decrease heat generatingat the switch circuit unit.

Herein, the LED channel may include one or more LEDs.

Herein, the n^(th) LED channel may have a different forward voltage Vfso as to reduce the power consumption at the n^(th) switch.

Herein, a saturation current of the (n−1)^(th) switch may be set greaterthan a saturation current of the n^(th) switch.

Herein, a voltage applied to the current sensing resistor may be changedby a sum of a current flowing through the n^(th) switch and a currentflowing through the (n+1)^(th) switch adjacent to the n^(th) switch.When the input voltage is equal to or greater than the forward voltageVf of the (n+1)^(th) LED channel to flow a saturation current throughthe (n+1)^(th) switch, the n^(th) switch may turn off.

Herein, the LED lighting device further may include a plurality of LEDoperation units. Each of the LED operation units may include therectifier circuit unit, the LED unit, the current sensing resistor, andthe switch circuit unit. Each of the plurality of the LED operationunits may be connected in parallel to the power source unit.

Herein, the plurality of the LED operation units may include a rectifiercircuit unit which outputs a same or different voltage according to theinput power of the same power source unit.

Herein, the LED unit may be formed as blocks and the LED lighting devicemay have a matrix connection structure. The LED lighting device mayfurther include a block connection unit to form a specific connectionstructure when the LED unit formed as the blocks are connected.

Herein, the LED lighting device further include a plurality of the LEDunits each formed as blocks which are connected in parallel.

Herein, the LED channel may be formed as a block having one or moreLEDs.

Herein, the LED unit may include capacitors, each connected in parallelto each of the LED channels. Furthermore, the capacitor may supply avoltage to the LED channel connected in parallel, when the input voltageis inputted as a voltage with which the LED channels connected inparallel are not operated.

Herein, the LED lighting device may further include, a current controlunit comprising a temperature sensor, which measures temperature of theswitch circuit unit, and controlling a current flowing through theswitch circuit unit according to the temperature of the switch circuitunit. Furthermore, a malfunction temperature may be set in the currentcontrol unit. The current control unit may protect the switch circuitunit through current control with which the switches are controlled soas not to flow a current through the switch circuit unit, when thetemperature of the switch circuit unit is equal to or greater than themalfunction temperature.

Herein, the LED lighting device may further include: a switch circuitcurrent blocking unit connected in series to the resistor unit forsensing and blocking a current, which flows through the switch circuitunit. Furthermore, a stable operation current value with which theswitch circuit unit is stably operated may be set in the switch circuitcurrent blocking unit. When the current flowing through the switchcircuit current blocking unit is greater than the stable operationcurrent value, the switch circuit current blocking unit may block theswitch through the current flows among the switches in the switchcircuit unit to block a current flowing through the switch circuit unit.

Herein, the LED lighting device may further include: a currentconversion switch positioned between the resistor unit and the lastswitch for blocking the current, which flows through the switch circuitunit; and a current blocking control unit for controlling the currentconversion switch, when an over-current flows through the switch circuitunit, to block the current flowing through the switch circuit unit.Furthermore, a stable operation current value with which the switchcircuit unit may be stably operated is set in the current blockingcontrol unit. When the current flowing through the switch circuit unitis greater than the stable operation current value, the current blockingcontrol unit may control the current conversion switch to block acurrent flowing through the switch circuit unit.

According to another aspect of the present invention, an LED lightingdevice, including: a rectification circuit unit for receiving an inputpower from a power source unit and outputting a rectified power; an LEDunit having a plurality of LED channels connected in series and aresistor unit connected to the last end of the LED channels; a dimmingcontrol unit comprising a variable resistor for controlling the currentflowing through the LED unit to control dimming of the LED channel; anda switch circuit unit comprising a plurality of switches, wherein ann^(th) switch is connected to the rear end of an n^(th) LED channel soas to control an operation of the LED channel, and is controlled by asum of a current of the n^(th) switch and a current of an (n+1)^(th)switch, which flows through the variable resistor.

Herein, the dimming control unit may further include a dimming controlswitch. The dimming control unit may perform dimming control by changingthe resistance value of the variable resistor with the switch to controlthe operating number of the LED channel of the LED unit. In addition,the dimming control unit may further include a dimming control switch.The dimming control unit may perform dimming control by changing theresistance value of the variable resistor with the switch to control thecurrent value flowing through the LED channel of the LED unit.

According to another aspect of the present invention, an LED lightingdevice, including: a rectification circuit unit for receiving an inputpower from a power source unit and outputting a rectified power; acharge storage circuit unit, receiving power from the rectifier circuitunit, storing charges at a high voltage, and outputting the storedcharges at low voltage; an LED unit having a plurality of LED channelsconnected in series and a resistor unit connected to the last end of theLED channels; a current sensing resistor; and a switch circuit unitcomprising a plurality of switches, wherein an n^(th) switch isconnected to the rear end of an n^(th) LED channel so as to control anoperation of the LED channel, and is controlled by a sum of a current ofthe n^(th) switch and a current of an (n+1)^(th) switch, which flowsthrough the current sensing resistor.

Herein, the charge storage circuit unit may include a first condenser, asecond condenser, a first diode, a second diode, and a third diode. Thesecond diode may be connected in a forward direction between the firstcondenser and the second condenser, an end of the first condenser may beconnected to a power source voltage node of the rectifier circuit unit,an end of the second condenser may be connected to a ground, the firstdiode may be connected in a backward direction between a ground and anode to which the first condenser and the second diode are connected,and the third diode may be connected between the LED unit and a node towhich the second condenser and the second diode are connected. Thecharge storage circuit unit may output the stored charges to supply avoltage to the LED unit when a voltage outputted from the rectifiercircuit unit is lower than a voltage stored in the charge storagecircuit unit.

According to another aspect of the present invention, an LED lightingdevice, including: a rectification circuit unit for receiving an inputpower from a power source unit and outputting a rectified power; aripple elimination circuit unit, receiving the input power, storingcharges, and outputting the stored charges to output ripple eliminatedpower when the input power decreases; an LED unit having a plurality ofLED channels connected in series and a resistor unit connected to thelast end of the LED channels; a current sensing resistor: and a switchcircuit unit comprising a plurality of switches, wherein an n^(th)switch is connected to the rear end of an n^(th) LED channel so as tocontrol an operation of the LED channel, and is controlled by a sum of acurrent of the n^(th) switch and a current of an (n+1)^(th) switch,which flows through the current sensing resistor.

Herein, the ripple elimination circuit unit may include a resistor and acapacitor, and output the charges stored in the capacitor when the inputpower decreases.

Advantageous Effects

According to some embodiment of the present invention, the LED lightingdevice includes a resistor end distributing heat of the switch unit soas to prevent the excessive heat generation at the switch unit, when avoltage equal to or greater than the rated voltage is inputted.Therefore, the LED lighting device provides an effect of maintaining thenormal operation of the switch unit formed of IC.

In addition, according to some embodiment of the present invention,since the forward voltage of the LED channel is redistributed, the LEDlighting device provides effects of decrease in the power consumption atthe switch unit and efficiency increase.

In addition, according to some embodiment of the present invention, theLED lighting device provides an effect that the dimming control isperformed by controlling the operation number of the LED or theoperation current of the LED by using the variable resistor.

In addition, according to some embodiment of the present invention, theLED lighting device provides an effect of providing a constantbrightness by the reduction of a flicker phenomenon caused by the inputvoltage.

In addition, according to some embodiment of the present invention, theLED lighting device provides an effect of the protection of the switchunit by blocking an over-current flowing through the switch unit.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a structure of a lighting device reducingthe heat generation at a switch unit, when a voltage equal to or greaterthan a rated voltage is inputted, according to some embodiment of thepresent invention.

FIG. 2 is a diagram showing voltages applied to the positions of LEDchannels according to input voltages, according to some embodiment ofthe present invention.

FIG. 3 is a diagram showing the power consumption at the switch unit,according to some embodiment of the present invention.

FIG. 4 is a diagram showing a structure of an LED lighting device havingone LED operation unit, according to some embodiment of the presentinvention.

FIG. 5 is a diagram showing a structure in which LED operation units areconnected in series, according to some embodiment of the presentinvention.

FIG. 6 is a diagram showing a structure in which LED operation units areconnected in parallel, according to some embodiment of the presentinvention.

FIG. 7 is a diagram showing operation of an LED operation unit accordingto the amount of the input voltage, according to some embodiment of thepresent invention.

FIG. 8 is a diagram showing a basic structure of a LED lighting device,according to some embodiment of the present invention.

FIG. 9 is a diagram showing a structure in which a plurality of LEDoperation units are connected to a power source unit, according to someembodiment of the present invention.

FIG. 10 is a diagram showing a structure of an LED lighting devicehaving one LED operation unit, according to some embodiment of thepresent invention.

FIG. 11 is a diagram showing a circuit structure having one or more LEDoperation units, according to some embodiment of the present invention.

FIG. 12 and FIG. 13 are diagrams showing structures of LED channelshaving one or more LEDs, according to some embodiment of the presentinvention.

FIG. 14 is a diagram showing a structure of a lighting device in whichthe heat generation at a switch unit decreases, when a voltage equal toor greater than the rated voltage is inputted, according to someembodiment of the present invention.

FIG. 15 is a diagram showing currents applied to the positions of LEDchannels according to input voltages, according to some embodiment ofthe present invention.

FIG. 16 is a diagram showing a dimming control by changing a currentvalue flowing through an LED channel, according to some embodiment ofthe present invention.

FIG. 17 is a diagram showing a structure of an LED lighting device inwhich a capacitor is connected in parallel to a LED channel to prevent aflicker phenomenon, according to some embodiment of the presentinvention.

FIG. 18 is a diagram showing the operation of an LED channel accordingto an input voltage, according to some embodiment of the presentinvention.

FIG. 19 is a diagram showing a brightness change according to an inputvoltage, according to some embodiment of the present invention.

FIG. 20 is a diagram showing a structure of an LED lighting devicehaving a circuit to reduce a flicker phenomenon, according to someembodiment of the present invention.

FIG. 21 is a diagram showing a structure and a function of a chargestorage circuit unit, according to some embodiment of the presentinvention.

FIG. 22 is a diagram showing the amount of a voltage supplied to an LEDoperation unit, according to some embodiment of the present invention.

FIG. 23 is a diagram showing a structure of an LED lighting devicehaving a circuit to eliminate ripple, according to some embodiment ofthe present invention.

FIG. 24 is a diagram showing a voltage inputted to an LED operation unitby a ripple elimination circuit unit, according to some embodiment ofthe present invention.

FIG. 25 is a diagram showing brightness without a ripple eliminationcircuit unit, according to some embodiment of the present invention.

FIG. 26 is a diagram showing brightness with a ripple eliminationcircuit unit, according to some embodiment of the present invention.

FIG. 27 is a diagram showing a structure of an LED lighting deviceprotecting a switch unit by current control, according to someembodiment of the present invention.

FIG. 28 is a diagram showing currents applied to the positions of LEDchannels according to an input voltage, according to some embodiment ofthe present invention.

FIG. 29 is a diagram showing a temperature control of a switch controlunit by controlling a current of a switch unit, according to someembodiment of the present invention.

FIG. 30 is a diagram showing a structure of a LED lighting deviceprotecting a switch unit by controlling a current of the switch unit,according to some embodiment of the present invention.

FIG. 31 is a diagram showing currents applied to the positions of LEDchannels according to an input voltage, according to some embodiment ofthe present invention.

FIG. 32 is a diagram showing the blockage of a current flowing through aswitch unit, when an input voltage equal to or greater than the ratedvoltage is inputted, according to some embodiment of the presentinvention.

FIG. 33 is a diagram showing a structure of a LED lighting deviceprotecting a switch unit by controlling a current, according to someembodiment of the present invention.

FIG. 34 is a diagram showing a current blocking control unit positionedbetween a switch unit and a current sensing resistor, according to someembodiment of the present invention.

FIG. 35 is a diagram showing currents applied to the positions of LEDchannels according to an input voltage, according to some embodiment ofthe present invention.

FIG. 36 is a diagram showing the blockage of a current flowing through aswitch unit, when an input voltage equal to or greater than the ratedvoltage is inputted, according to some embodiment of the presentinvention.

DESCRIPTION OF REFERENCE NUMERALS

-   -   10: power source unit 20: rectifier circuit unit    -   30: LED unit    -   31, 32, 33, 34, 35, 36, 37: LED channel    -   38: resistor unit    -   40: switch unit    -   41, 42, 43, 44, 45, 46, 47, 48: switch    -   50: current sensing resistor

BEST MODE

Hereinafter, the present invention will now be described more fully withreference to the accompanying drawings, in which exemplary embodimentsof the invention are shown. While the present invention has beenparticularly shown and described with reference to exemplary embodimentsthereof, it will be understood by those of ordinary skill in the artthat various changes in form and details may be made therein withoutdeparting from the spirit and scope of the present invention. However,the present invention is not limited by the embodiments described later,but realized with various aspects. The embodiments in this descriptionwill make the disclosures of the present invention complete, and providethe scope of the invention to those of ordinary skill in the art.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the presentinvention. It will be understood that the terms first, second, third,etc., are only used to distinguish one component from another component.In addition, the singular forms “a,” “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise.

Hereinafter, embodiments of the present invention will be described indetail with reference to accompanying drawings.

FIG. 1 is a diagram showing a structure of a lighting device reducingthe heat generation at a switch unit, when a voltage equal to or greaterthan a rated voltage is inputted, according to some embodiment of thepresent invention.

The lighting device of the present invention includes a rectifiercircuit unit 20, an LED unit 30, a switch unit 40 and a current sensingresistor 50.

An the power source unit 10 supplies an input power. The rectifiercircuit unit 20 receives the input power from the power source unit 10,rectifies the input power, and outputs a rectified power.

The LED unit 30 includes n LED channels connected in series, and aresistor unit 38 is connected to the last end of the last LED channel.

In FIG. 1, for example, the LED unit 30 includes 7 LED channels 31, 32,33, 34, 35, 36, 37. The resistor unit 38 is connected to an end next tothe last LED channel 37 among the LED channels connected each other inseries.

The switch unit 40 includes n+1 switches to operate the LED channelsaccording to the input power source. Herein, the n switches among then+1 switches controls the operations of the LED channels according tothe input power source, and the (n+1)^(th) switch operates the resistorunit 38.

In FIG. 1, for example, the second LED channel 32 and the first switch41 are connected to an end next to the first LED channel 31. The thirdLED channel 33 and the second switch 42 are connected to an end next tothe second LED channel 32. The fourth LED channel 34 and the thirdswitch 43 are connected to an end next to the third LED channel 33. Thefifth LED channel 35 and the fourth switch 44 are connected to an endnext to the fourth LED channel 34. The six LED channel 36 and the fifthswitch 45 are connected to an end next to the fifth LED channel 35. Theseventh LED channel 37 and the sixth switch 46 are connected to an endnext to the sixth LED channel 36. The resistor unit 38 and the seventhswitch 47 are connected to an end next to the seventh LED channel 37.The eighth switch 48 is connected to an end next to the resistor unit38.

Herein, each of the switches consists of a FET (Field EffectTransistor), for example, a NMOS FET.

The current sensing resistor 50 is connected to each of the switches 41,42, 43, 44, 45, 46, 47, 48 included in the switch unit 40. Thus, whencurrents flow through the switches, the current flowing through thecurrent sensing resistor 50 is a sum of the currents flowing through theswitches.

According to the present invention, the LED channels operate accordingto the amount of the input power source. A corresponding LED channeloperates according to the amount of the rectified power source inputtedthe LED unit 30.

The operation of the switch unit 40 according to the present inventionwill be described.

Initially, an operation voltage is inputted to gates of all switches 41,42, 43, 44, 45, 46, 47, 48 to operate each switch (that is, the currentflows). Herein, the condition of Vgs1<Vgs2<Vgs3<Vgs4<Vgs5<Vgs6<Vgs7 issatisfied. Each of Vgs1, Vgs2, Vgs3, Vgs4, Vgs5, Vgs6, and Vgs7 isconnected to the current sensing resistor 50 and affected by a voltageapplied to the current sensing resistor 50.

Afterward, the switches in the switch unit 40 are automaticallycontrolled by the voltage value applied to the current sensing resistor50 according to the amount of the rectified voltage inputted in the LEDunit 30, thereby operating the LED channels. In the present invention, aswitching condition means that when current flows two adjacent switches,a voltage is generated at the current sensing resistor by a sum of thecurrents flowing through the two adjacent switches, the operationvoltage decreases due to the voltage applied to the current sensingresistor, and then any switch having a lower operation voltage firstturns off.

For example, the current sensing resistor is set for 10 ohm.

Table 1 shows saturation current values at the switches (FETs) andvoltages applied to the current sensing resistor when the saturationcurrent flows through switches.

Herein, “Id” indicates a saturation current of the corresponding switch.It indicates a saturation voltage when the switch operates and a currentflows. “Vrs” indicates a voltage applied to the current sensingresistor.

TABLE 1 Id (mA) Vrs First FET 20 0.2 Second FET 40 0.4 Third FET 60 0.6Fourth FET 80 0.8 Fifth FET 100 1.0 Sixth FET 120 1.2 Seventh FET 1401.4 Eighth FET 160 1.6

In addition, a forward voltage Vf of each LED channel is 30V.

In this case, when an input voltage increases to reach about 30V, thefirst LED channel 31 begins to operate and a current I1 begins to flowthrough the first switch 41. When the input voltage is equal to orgreater than 30V, a saturation current of 20 mA flows through the firstswitch 41 and the voltage applied to the current sensing resistorbecomes 0.2V.

When the input voltage increases to reach about 60V, the second LEDchannel 32 begins to operate and a current I2 gradually flows throughthe second switch 42. A current flowing through the current sensingresistor 50 is a sum of the current flowing through the first switch 41of 20 mA and the current I2 flowing through the second switch 42. Thus,the voltage at the current sensing resistor 50 gradually increases. Asthe voltage applied to the current sensing resistor 50 increases, thevoltage Vgs1 inputted to the gate of the first switch 41 becomesrelatively lower, and thus the first switch 41 gets into the switchingcondition in which an on-state changes to an off-state. When the inputvoltage gradually increases to gradually increase the current I2 flowingthrough the second switch 42, the voltage applied to the current sensingresistor 50 gradually increases to lower the voltage value of Vgs1, andthus the first switch 41 becomes the off-state.

When the input voltage is equal to or greater than 60V, a saturationcurrent of 40 mA flows through the second switch 42 and the first switch41 is completely the off-state.

When the input voltage increases to reach about 90V, the third LEDchannel 33 begins to operate, a current I3 gradually flows through thethird switch 43. Herein, a current flowing through the current sensingresistor 50 is a sum of the currents flowing through the second switch42 of 40 mA and the current I3 flowing through the third switch 43.Thus, the voltage applied to the current sensing resistor 50 graduallyincreases. As the voltage applied to the current sensing resistor 50increases, the voltage Vgs2 inputted to the gate of the second switch 42becomes relatively lower, and thus the second switch 42 gets into theswitching condition in which an on-state changes to an off-state. Whenthe voltage value applied to the current sensing resistor 50 graduallyincreases to lower the voltage value of Vgs2, and thus the second switch42 becomes the off-state.

When the input voltage is equal to or greater than 90V, a saturationcurrent of 60 mA flows through the third switch 43, and the secondswitch 42 becomes completely the off-state.

As described above, when a current sequentially flows through a(n+1)^(th) switch according to the input voltage, a n^(th) switchbecomes the off-state.

When the input voltage increases to reach about 210V, the seventh LEDchannel 37 begins to operate, and a current I7 and a current I8gradually flow through the seventh switch 47 and the eighth switch 48,respectively. Herein, a current flowing through the current sensingresistor 50 is a sum of the currents flowing through the sixth switch 46of 120 mA and the currents flowing through the seventh switch 47 and theeighth switch 48. Likewise, when the input voltage is equal to orgreater than 210V, a saturation current of 140 mA flows through theseventh switch 47, and the sixth switch 46 becomes completely theoff-state.

However, when the input voltage is equal to or greater than 210V andequal to or greater than the rated voltage, the seventh switch 47becomes the off-state and only the eighth switch 48 operates because ofthe same reason.

Herein, in case that an LED is connected at the position of the resistorunit 38 instead of the resistor according to the conventional art, whenthe input voltage equal to or greater than the rated voltage isinputted, an over-current flows through the eighth switch 48, therebygenerating a lot of heat. That is, an over-current flows through theswitch operating the last LED channel. Thus, the generation of theoverheating harmfully affects the switch unit 40 formed of IC componentsto cause a breakdown of the components and efficiency reduction due tothe heat generation.

Thus, according to the present invention, since the resistor unit 38 isconnected and the voltage is distributed to the resistor unit 38, when avoltage equal to or greater than the rated voltage is inputted, the heatgenerated at the eighth switch 48 is distributed to the resistor unit38, thereby preventing the eighth switch 48 from overheating. In thisway, according to the present invention, when the input voltage equal toor greater than the rated voltage is inputted, the switch unit 40 is notoverheated, thereby providing the stability of the switch unit 40 formedof the IC.

In addition, according to the present invention, a capacitor may beconnected between the rectifier circuit unit 20 and each of the LEDchannels 31, 32, 33, 34, 35, 36, 37, thereby preventing a flickerphenomenon.

FIG. 2 is a diagram showing voltages applied to the positions of LEDchannels according to input voltages, according to some embodiment ofthe present invention. FIG. 3 is a diagram showing the power consumptionat the switch unit, according to some embodiment of the presentinvention.

As shown in FIG. 2, the voltage of the LED unit 30 according to theinput voltage A forms a step functional voltage B due to the forwardvoltage of each of the LED channels. Herein, “{circle around (1)}”indicates the voltage applied to the LED unit 30 when the first LEDchannel operates. “{circle around (2)}” indicates the voltage applied tothe LED unit 30 when the second LED channel operates. “{circle around(3)}” indicates the voltage applied to the LED unit 30 when the thirdLED channel operates. “{circle around (4)}” indicates the voltageapplied to the LED unit 30 when the fourth LED channel operates.“{circle around (5)}” indicates the voltage applied to the LED unit 30when the fifth LED channel operates. “{circle around (6)}” indicates thevoltage applied to the LED unit 30 when the sixth LED channel operates.“{circle around (7)}” indicates the voltage applied to the LED unit 30when the seventh LED channel operates. “{circle around (8)}” indicatesthe voltage applied to the LED unit 30 when a current flows through theeighth switch.

Herein, when a voltage equal to or greater than the rated voltage (forexample, a voltage greater than 110% or more of the input voltage) isinputted, the voltage applied to the LED unit 30 increases. When avoltage equal to or greater than the rated voltage is inputted, thevoltage applied to the LED unit 30 increases, thereby a current flowingthrough the switch connected to the last end increases.

As the current increase, the power increases proportional to a square ofthe current.

FIG. 3 is a diagram showing power consumption at the switch unit 40according to the operating LED channels, according to some embodiment ofthe present invention.

FIG. 3(a) is a diagram showing the power consumption at the switch unit40 when the forward voltages of the LED channels are constant and an LEDis connected instead of the resistor unit 38. “1” indicates the powerconsumption when a current flows through the first switch 41. “2”indicates the power consumption when a current flows through the secondswitch 42. “3” indicates the power consumption when a current flowsthrough the third switch 43. “4” indicates the power consumption when acurrent flows through the fourth switch 44. “5” indicates the powerconsumption when a current flows through the fifth switch 45. “6”indicates the power consumption when a current flows through the sixthswitch 46. “7” indicates the power consumption when a current flowsthrough the seventh switch 47. “8” indicates the power consumption whena current flows through the eighth switch 48 and a voltage equal to orgreater than the rated voltage is inputted.

From the first switch to the seventh switch, when the input voltageincreases, the n^(th) switch is operated by the remained voltage formedby subtracting the forward voltage at the n^(th) LED channel. When themore voltage is inputted, the n^(th) switch becomes the off-state andthe (n+1)^(th) switch operates, thereby increasing the power consumption(heat generation). However, the power consumption is within a range ofno more than 0.3. When a voltage equal to or greater than the ratedvoltage is inputted, an excessive current flows through the eighthswitch 48 (the last switch), and then the power consumption (heatgeneration) becomes greater than 1. Thus, when the voltage equal to orgreater than the rated voltage is inputted, overheating occurs at theeighth switch 48.

According to the present invention, since the resistor unit 38 isincluded, heat can be generated at the resistor unit 38 when the voltageequal to or greater than the rated voltage is inputted, thereby reducingthe heat generating at the eighth switch 48.

In addition, according to the present invention, the forward voltages Vfof the LED channels are unevenly redistributed, and then the powerconsumed at each switch becomes almost same. That is, the forwardvoltage Vf of the (n+1)^(th) LED channel increases greater than theforward voltage Vf of the n^(th) LED channel, and then the powerconsumption at the n^(th) switch and the power consumption at the(n+1)^(th) switch become almost same. By the redistribution of theforward voltages Vf of the LED channels, the heat generation at theswitch unit 40 becomes same regardless of the change of the inputvoltage.

FIG. 3(b) is a diagram showing that the power consumption at the switchunit 40 is equal to or less than 0.2 by the redistribution of theforward voltages of each LED channel even when the input voltageincreases. Herein, although the forward voltage Vf of each LED channelcan be freely changed, the total amount of the forward voltages Vf isset according to the maximum value of the input voltage.

In addition, in FIG. 3(b), since the resistor unit 38 is included, thepower consumption at the eighth switch 48 (the last switch) is same asthat at other switches even when the input voltage is equal to orgreater than the rated voltage.

The lighting device of the present invention described above hasadvantages as follows.

The FET switches can be automatically switched according to the inputvoltage without any input voltage sensing circuit or any input periodsensing circuit. In addition, since the switch unit can be simplyformed, additional LED channels can be added in the same area. Inaddition, since the forward voltage Vf at each LED channel can becontrolled and redistributed, the efficiency of the switch unitincreases and the combination of LEDs can be freely performed.

Otherwise, in a modified example of this embodiment, a ghost lightprevention resistor (not shown) can be included at the position of thefirst switch 41 after removing the first LED 31 in order to prevent thegeneration of ghost light. For example, a secondary lighting device,which provides weak light when an ON/OFF switch is off, can be added inorder to the position of the ON/OFF switch of the LED lighting device.In case of no ghost light prevention resistor, there is a problem thatthe first LED 31 of the LED unit 30 may emit light through the emittinglight path of the secondary lighting device even when the ON/OFF switchis off in case of no ghost light prevention resistor. To solve thisproblem, the first LED 31 is removed and a ghost light preventionresistor is added at the position of the first switch 41, therebyproviding a current path through the ghost light prevention resistor andpreventing the generation of ghost light. This type of the ghost lightprevention structure can be similarly applied to following embodiments.

FIG. 4 is a diagram showing a structure of an LED lighting device havingone LED operation unit, according to some embodiment of the presentinvention.

The power source unit 10 supplies the input power. Since the powersource unit 10 uses an alternating current (AC) power source, the amountof the input voltage is periodically changed as time passes. Therectifier circuit unit 20 receives the AC input power from the powersource unit 10, rectifies the input power, and outputs a rectifiedpower.

The LED operation unit includes the LED unit 30, the switch unit 40, andthe current sensing resistor 50. The LED unit 30 receives the power fromthe rectifier circuit unit 20 to perform the operation. The plurality ofthe LED channels are connected in series, and a resistor unit 35 isconnected to a lower portion of the last LED channel.

Hereinafter, the present invention will be described with an assumptionof n=4 for easy description.

The switch unit 40 includes a plurality of the switches 41, 42, 43, 44,45. The n^(th) switch is connected to the rear end of the n^(th) LEDchannel so as to control an operation of the LED channel. The n^(th)switch is controlled by a sum of a current of the n^(th) switch and acurrent of the (n+1)^(th) switch, which flows through the currentsensing resistor 50.

The current sensing resistor 50 is connected to each of the switches 41,42, 43, 44, 45 included in the switch unit 40. Thus, when currents flowthrough the switches, the current flowing through the current sensingresistor 50 is a sum of the currents flowing through the switches.

In FIG. 4, for example, the second LED channel 32 and the first switch41 is connected to an end next to the first LED channel 31. The thirdLED channel 33 and the second switch 42 is connected to an end next tothe second LED channel 32. The fourth LED channel 34 and the thirdswitch 43 is connected to an end next to the third LED channel 33. Theresistor unit 35 and the fifth switch 44 is connected to an end next tothe fourth LED channel 34. The fifth switch 45 is connected to an endnext to the resistor unit 35.

Herein, each of the switches consists of a FET (Field EffectTransistor), for example, a NMOS FET.

The current sensing resistor 50 is connected to each of the switches 41,42, 43, 44, 45 included in the switch unit 40. Thus, when currents flowthrough the switches, the current flowing through the current sensingresistor 50 is a sum of the currents flowing through the switches.

The current sensing resistor 50 may consist of a variable resistor.

According to the present invention, the LED channels operate accordingto the amount of the input power source. A corresponding LED channeloperates according to the amount of the rectified power source inputtedthe LED unit 30.

The operation of the switch unit 40 according to the present inventionwill be described.

Initially, an operation voltage is inputted to gates of all switches 41,42, 43, 44, 45 to operate each switch (that is, the current flows).

Herein, an operation voltage of the first switch 41 is Vgs1, anoperation voltage of the second switch 42 is Vgs2, an operation voltageof the third switch 43 is Vgs3, an operation voltage of the fourthswitch 44 is Vgs4, and an operation voltage of the fifth switch 45 isVgs5.

Herein, the condition of Vgs1<Vgs2<Vgs3<Vgs4<Vgs5 is satisfied.

Each of Vgs1, Vgs2, Vgs3, Vgs4, and Vgs5 is connected to the currentsensing resistor 50 and affected by a voltage applied to the currentsensing resistor 50.

Afterward, the switches in the switch unit 40 are automaticallycontrolled by the voltage value applied to the current sensing resistor50 according to the amount of the rectified voltage inputted in the LEDunit 30, thereby operating the LED channels.

In the present invention, a switching condition means that when currentflows two adjacent switches, a voltage is generated at the currentsensing resistor by a sum of the currents flowing through the twoadjacent switches, the operation voltage decreases due to the voltageapplied to the current sensing resistor, and then any switch having alower operation voltage first turns off.

Afterward, the switches in the switch unit 40 are automaticallycontrolled by the voltage value applied to the current sensing resistor50 according to the amount of the rectified voltage inputted in the LEDunit 30, thereby operating the LED channels.

In the present invention, for example, the current sensing resistor 50is set for 10 ohm.

Table 2 shows saturation current values at the switches (FETs) andvoltages applied to the current sensing resistor when the saturationcurrent flows through switches.

Herein, “Id” indicates a saturation current of the corresponding switch.It indicates a saturation voltage when the switch operates and a currentflows. “Vrs” indicates a voltage applied to the current sensingresistor.

TABLE 2 Id (mA) Vrs First FET 20 0.2 Second FET 40 0.4 Third FET 60 0.6Fourth FET 80 0.8 Fifth FET 100 1.0

In addition, a forward voltage Vf of each LED channel is 50V.

In this case, when the input voltage increases to reach about 50V, thefirst LED channel 31 begins to operate and a current I1 gradually flowsthrough the first switch 41. When the input voltage is equal to orgreater than 50V, a saturation current of 20 mA flows through the firstswitch 41 and the voltage applied to the current sensing resistor 50becomes 0.2V.

When the input voltage increases to reach about 100V, the second LEDchannel 32 begins to operate and a current I2 gradually flows throughthe second switch 42. A current flowing through the current sensingresistor 50 is a sum of the currents flowing through the first switch 41of 20 mA and the current I2 flowing through the second switch 42. Thus,the voltage applied to the current sensing resistor 50 graduallyincreases. As the voltage applied to the current sensing resistor 50increases, the voltage Vgs1 inputted to the gate of the first switch 41becomes relatively lower, and thus the first switch 41 gets into theswitching condition in which an on-state changes to an off-state. Whenthe input voltage gradually increases to gradually increase the currentI2 flowing through the second switch 42, the voltage applied to thecurrent sensing resistor 50 gradually increases to relatively lower thevoltage value of Vgs1, and thus the first switch 41 becomes theoff-state.

When the input voltage is equal to or greater than 100V, a saturationcurrent of 40 mA flows through the second switch 42 and the first switch41 is completely the off-state.

When the input voltage increases to reach about 150V, the third LEDchannel 33 begins to operate, a current I3 gradually flows through thethird switch 43. Herein, a current flowing through the current sensingresistor 50 is a sum of the currents flowing through the second switch42 of 40 mA and the current I3 flowing through the third switch 43.Thus, the voltage applied to the current sensing resistor 50 graduallyincreases. As the voltage applied to the current sensing resistor 50increases, a voltage Vgs2 inputted to the gate of the second switch 42becomes relatively lower, and thus the second switch 42 gets into theswitching condition in which an on-state changes to an off-state. Whenthe voltage value applied to the current sensing resistor 50 graduallyincreases to relatively lower the voltage value of Vgs2, and thus thesecond switch 42 becomes the off-state.

When the input voltage is equal to or greater than 150V, a saturationcurrent of 60 mA flows through the third switch 43, and the secondswitch 42 becomes completely the off-state.

As described above, when a current sequentially flows through a(n+1)^(th) switch according to the input voltage, a n^(th) switchbecomes the off-state.

When the input voltage increases to reach about 200V, the fourth LEDchannel 34 begins to operate, and the current I3 and a current I4gradually flow through the third switch 43 and the fourth switch 44,respectively. Herein, a current flowing through the current sensingresistor 50 is a sum of the currents flowing through the third switch 43of 60 mA and the currents flowing through the fourth switch 44 and thefifth switch 45.

Likewise, when the input voltage is greater than 200V, a saturationcurrent of 80 mA flows through the fourth switch 44, and the thirdswitch 43 becomes completely the off-state.

However, when the input voltage equal to or greater than the ratedvoltage is inputted (for example, the voltage of about 250V), the fourthswitch 44 becomes the off-state and only the fifth switch 48 operatesbecause of the same reason.

Herein, in case that an LED is connected at the position of the resistorunit 35 instead of the resistor according to the conventional art, whenthe input voltage equal to or greater than the rated voltage isinputted, an over-current flows through the eighth switch 45, therebygenerating a lot of heat. That is, an over-current flows through theswitch operating the last LED channel. Thus, the generation of theoverheating harmfully affects the switch unit 40 formed of IC componentsto cause a breakdown of the components and efficiency reduction due tothe generation of the heat.

Thus, according to the present invention, since the resistor unit 35 isconnected to the last end of the LED unit 30 and the voltage isdistributed at the resistor unit 35, when a voltage equal to or greaterthan the rated voltage is inputted, the heat generated at the fifthswitch 45 is distributed to the resistor unit 35, thereby preventing thefifth switch 45 from overheating. In this way, according to the presentinvention, when the input voltage equal to or greater than the ratedvoltage is inputted, some of the overheat generated at the switch unit40 is distributed to the resistor unit 35 to be heated, thereby reducingthe overheat at the switch unit 40 formed of the IC and providing thestability of the switch unit 40.

In addition, the present invention has distinguishable featuresaccording to the power consumption.

From the first switch to the fourth switch, when the input voltageincreases, the n^(th) switch is operated by the remained voltage formedby subtracting the forward voltage at the n^(th) LED channel. When morevoltage is inputted, the n^(th) switch becomes the off-state and the(n+1)^(th) switch operates so as to increase the power consumption (heatgeneration). However, the total power consumption is within a specificsystem standard range. When a voltage equal to or greater than the ratedvoltage is inputted, an excessive current flows through the fifth switch45 (the last switch), and then the power consumption (heat generation)becomes greater than the system standard range. Thus, when the voltageequal to or greater than the rated voltage is inputted, overheatingoccurs at the fifth switch 45.

According to the present invention, since the resistor unit 35 isincluded, heat can be generated at the resistor unit 35, even when thevoltage equal to or greater than the rated voltage is inputted, therebyreducing the heat generating at the fifth switch 45.

In addition, according to the present invention, the forward voltages Vfof the LED channels are unevenly redistributed, and then the powerconsumed at each switch becomes almost same. That is, the forwardvoltage Vf of the (n+1)^(th) LED channel increases greater than theforward voltage Vf of the n^(th) LED channel, and then the powerconsumption at the n^(th) switch and the power consumption at the(n+1)^(th) switch become almost same. By the redistribution of theforward voltages Vf of the LED channels, the heat generation at theswitch unit 40 becomes same regardless of the change of the inputvoltage.

Herein, although the forward voltage Vf of each LED channel can befreely changed, the total amount of the forward voltages Vf is set asthe maximum value of the input voltage.

FIG. 5 is a diagram showing a structure in which LED operation units areconnected in series, according to some embodiment of the presentinvention.

According to the present invention, LED operation units are connected inseries, as shown in FIG. 5.

FIG. 5 shows an LED lighting device includes two LED operation units100, 200 connected each other in series.

Each of the LED operation units 100, 200 includes the LED unit 30, theswitch unit 40 and the current sensing resistor 50, as shown in FIG. 4.

As shown in FIG. 5, when the LED operation units 100, 200 are connectedin series, the maximum voltage of the input voltage is Vmax. When theLED units in the first LED operation unit 100 and the second LEDoperation unit 200 use LEDs having the same forward voltages Vf, thefirst LED operation unit 100 performs its switching operation under avoltage within a range of (½) times Vmax of the input voltage, and thesecond LED operation unit 200 performs its switching operation under avoltage equal to or greater than (½) times Vmax of the input voltage.

When the maximum value of the input voltage is 220V and the inputvoltage is less than 110V, the LED unit 30 and the switch unit 40 in thefirst LED operation unit 100 performs the switching operation, as shownin FIG. 4.

That is, when the input voltage is from 110V to 220V, all LED channelsin the first LED operation unit 100 operates to emit light, and theswitching operation of the switch unit 40 and the operation of the LEDunit 30 in the second LED operation unit 200 performs the switchingoperation, as shown in FIG. 4.

When LED units in the first LED operation unit 100 and the LED units inthe second LED operation unit 200 use LEDs having different forwardvoltages Vf, the range of the input voltage operating each of LEDoperation units 100, 200 is changed according to the amount of theforward voltage Vf of each of the LED operation units 100, 200.

As shown in FIG. 5, when the LED operation units 100, 200 are connectedin series, brightness becomes twice with the input voltage greater thana predetermined voltage, compared with using one LED operation unit LEDoperation unit.

FIG. 6 is a diagram showing a structure in which LED operation units areconnected in parallel, according to some embodiment of the presentinvention.

According to the present invention, LED operation units are connected inparallel, as shown in FIG. 6.

FIG. 6 shows an LED lighting device includes two LED operation units300, 400 connected each other in parallel.

Each of the LED operation units 300, 400 includes the LED unit 30, theswitch unit 40 and the current sensing resistor 50, as shown in FIG. 4.The switching operation of the switch unit 40 and the operation of theLED unit 30 in each of LED operation units 300, 400 are same asdescribed in FIG. 4.

As shown in FIG. 6, when the LED operation units 300, 400 are connectedin parallel, and LED units in the first LED operation unit 300 and thesecond LED operation unit 400 use LEDs having the same forward voltagesVf, the first LED operation unit 300 and the second LED operation unit400 independently perform the same operation at the same amount of theinput voltage according to the amount of the input voltage V.

That is, the switching operation of the LED unit 30 and the switch unit40 in the first LED operation unit 300 and the switching operation ofthe LED unit 30 and the switch unit 40 in the second LED operation unit400 are the same within the same range of the input voltage, asdescribed in FIG. 4.

When LED units in the first LED operation unit 300 and the LED units inthe second LED operation unit 400 has LEDs having different forwardvoltages Vf, the range of the input voltage operating each of the LEDoperation units 300, 400 is changed according to the amount of theforward voltage Vf of each of the LED operation units 300, 400.

As shown in FIG. 6, when the LED operation units 300, 400 are connectedin parallel, brightness becomes twice with the input voltage greaterthan a predetermined voltage, compared with using one LED operation unitLED operation unit under the same power.

FIG. 7 is a diagram showing operation of an LED operation unit accordingto the amount of the input voltage, according to some embodiment of thepresent invention.

“V1” indicates an input voltage operating all LED channels in the firstLED operation unit. “V2” indicates the maximum value of the inputvoltage.

As shown in FIG. 5, when the first LED operation unit 100 and the secondLED operation unit 200 are connected in series, only the first LEDoperation unit 100 operates within V1 of the input voltage, as describedin FIG. 4. When the input voltage is equal to or greater than V1, all ofthe LED channels of the LED unit 30 in the first LED operation unit 100operates (emitting light), and the second LED operation unit 200operates according to the amount of the input voltage, as described inFIG. 4.

Thus, in the section A, only the first LED operation unit 100 performsthe switching operation, as described in FIG. 4, and then acorresponding LED channel operates according to the input voltage. Inthe section B, all LED channels in the first LED operation unit 100operate and only the second LED operation unit 200 performs theswitching operation, as described in FIG. 4, and then a correspondingLED channel operates according to the input voltage.

When the first LED operation unit 300 and the second LED operation unit400 are connected in parallel as shown in FIG. 6, the first LEDoperation unit 300 and the second LED operation unit 400 performs thesame operation described in FIG. 4 in at the same amount of the inputvoltage according to the input voltage.

The lighting device of the present invention described above hasadvantages as follows.

The FET switches can be automatically switched according to the inputvoltage without any input voltage sensing circuit or any input periodsensing circuit. In addition, since the switch unit can be simplyformed, additional LED channels can be added in the same area. Inaddition, since the forward voltage Vf at each LED channel can becontrolled and redistributed, the efficiency of the switch unitincreases and the combination of LEDs can be freely performed. Inaddition, when the plurality of the LED operation units are connected inseries, n times brightness can be used in the section in which then^(th) LED operation unit operates, compared with using one LEDoperation unit. In addition, when m LED operation units are connected inparallel, m times brightness can be used regardless of the amount of theinput voltage, compared with using one LED operation unit.

FIG. 8 is a diagram showing a basic structure of a LED lighting device,according to some embodiment of the present invention.

The lighting device of this embodiment includes the LED operation unit100 receiving from the power source unit 10. Herein, a plurality of LEDoperation units 100 are included, each of which is connected in parallelto the power source unit 10. However, in FIG. 8, one LED operation unit100 is connected to the power source unit 10 will be described in orderto describe the operation of the LED operation unit 100.

The power source unit 10 supplies the input power. Since the powersource unit 10 uses an AC power source, the amount of the input voltageis periodically changed as time passes.

The LED operation unit 100 includes the rectifier circuit unit 20, theLED unit 30, the switch unit 40, the current sensing resistor 50.

The rectifier circuit unit 20 receives the AC input power from the powersource unit 10, rectifies the input power, and outputs a rectifiedpower.

The LED unit 30 receives the power from the rectifier circuit unit 20 toperform the operation. The plurality of the LED channels are connectedin series, and the resistor unit 35 is connected to a lower portion ofthe last LED channel.

Hereinafter, the present invention will be described with an assumptionof n=4 for easy description.

The switch unit 40 includes a plurality of the switches 41, 42, 43, 44,45. The n^(th) switch is connected to the rear end of the n^(th) LEDchannel so as to control an operation of the LED channel. The n^(th)switch is controlled by a sum of a current of the n^(th) switch and acurrent of the (n+1)^(th) switch, which flows through the currentsensing resistor.

The current sensing resistor 50 is connected to each of the switches 41,42, 43, 44, 45 included in the switch unit 40. Thus, when currents flowthrough the switches, the current flowing through the current sensingresistor 50 is a sum of the currents flowing through the switches.

In FIG. 8, for example, the second LED channel 32 and the first switch41 are connected an end next to the first LED channel 31. The third LEDchannel 33 and the second switch 42 are connected an end next to thesecond LED channel 32. The fourth LED channel 34 and the third switch 43are connected an end next to the third LED channel 33. The resistor unit35 and the fourth switch 44 are connected an end next to the fourth LEDchannel. The fifth switch 45 is connected an end next to the resistorunit 35.

Herein, each of the switches consists of a FET (Field EffectTransistor), for example, a NMOS FET.

The current sensing resistor 50 is connected to each of the switches 41,42, 43, 44, 45 included in the switch unit 40. Thus, when a current flowthrough the switches, the current flowing through the current sensingresistor 50 is a sum of the currents flowing through the switches.

The current sensing resistor 50 may consist of a variable resistor.

According to the present invention, the LED channels operate accordingto the amount of the input power source. A corresponding LED channeloperates according to the amount of the rectified power source inputtedthe LED unit 30.

The operations of the switch unit 40, the current sensing resistor 50,and the resistor unit 35 according to this embodiment can be describedwith reference of the above description of FIG. 4.

Thus, according to the present invention, when the resistor unit 35 isconnected to the last end of the LED unit 30, the voltage is distributedat the resistor unit 35, and a voltage equal to or greater than therated voltage is inputted, the heat generated at the fifth switch 45 isdistributed to the resistor unit 35, thereby preventing the fifth switch45 from overheating. In this way, according to the present invention,when the input voltage equal to or greater than the rated voltage isinputted, some of the overheat generated at the switch unit 40 isdistributed to the resistor unit 35 to be heated, thereby reducing theoverheat at the switch unit 40 formed of the IC and providing thestability of the switch unit 40.

In addition, this embodiment has the same distinguishable features ofpower consumption as those in the embodiment of FIG. 4. Accordingly, asthe forward voltage Vf of the LED channel is redistributed, the heatgeneration at the switch unit 40 becomes same even when the inputvoltage is changed.

FIG. 9 is a diagram showing a structure in which a plurality of LEDoperation units are connected to a power source unit, according to someembodiment of the present invention.

According to the present invention, each of the LED operation units isconnected to the power source unit 10 in parallel, as shown in FIG. 9.

In FIG. 9, the LED lighting device includes three LED operation units100_1, 100_2, 100_3 connected each other in parallel.

Each of the LED operation units 100_1, 100_2, 100_3 includes therectifier circuit unit 20, the LED unit 30, the switch unit 40, and thecurrent sensing resistor 50, as described in FIG. 8. The switchingoperation of the switch unit 40 and the operation of the LED unit 30 ineach of the LED operation units 100_1, 100_2, 100_3 are same as thosedescribed in FIG. 8.

When the LED operation units 100_1, 100_2, 100_3 are connected inparallel and LEDs having the same forward voltage Vf are used in thefirst LED operation unit 100_1, the second LED operation unit 100_2, andthe third LED operation unit 100_3, as described in FIG. 9, each of thefirst LED operation unit 100_1, the second LED operation unit 100_2 andthe third LED operation unit 100_3 independently perform the sameoperation at the same amount of the input voltage according to theamount of the input voltage V.

When the LED units in the first LED operation unit 100_1 and the secondLED operation unit 100_2, and the third LED operation unit 100_3 hasLEDs having different forward voltages Vf, the range of the inputvoltage operating each of the LED operation units 100_1, 100_2, 100_3 ischanged according to the amount of the forward voltage Vf of each of theLED operation units 100_1, 100_2, 100_3.

As shown in FIG. 9, when the LED operation units 100_1, 100_2, 100_3 areconnected in parallel, brightness becomes three times, compared withusing one LED operation unit LED operation unit 100 under the samepower.

According to the present invention, each of the LED operation units100_1, 100_2, 100_3 is formed as a block structure, each block isconnected to a plurality of blocks for user's convenience, and then thelighting device performing automatic switching can be used in a widerrange. For example, when the lighting device is used for a stadium suchas a baseball stadium or a soccer stadium, the lighting device of thepresent invention has distinguishable features providing easy andconvenient use of the lighting device for the stadium with a pluralityof the LED operation units covering all range of the stadium.

The rectifier circuit units included in the plurality of the LEDoperation units 100_1, 100_2, 100_3 may be the same rectifier circuitunits or different rectifier circuit units having different outputvoltage ranges.

When the plurality of the LED operation units 100_1, 100_2, 100_3include the same rectifier circuit units, each of the LED operationunits 100_1, 100_2, 100_3 has the same lighting characteristicsaccording to the input voltage outputted from the power source unit 10.However, when the plurality of the LED operation units 100_1, 100_2,100_3 have different rectifier circuit units, the LED operation units100_1, 100_2, 100_3 has different lighting characteristics according tothe input voltage outputted from the power source unit 10. Thus, whendifferent lighting characteristics are required in an area (range), aplurality of the LED operation units 100_1, 100_2, 100_3 are formed toinclude different rectifier circuit units, thereby providing requiredlighting characteristics for the corresponding area.

The lighting device of the present invention described above hasadvantages as follows. The FET switches can be automatically switchedaccording to the input voltage without any input voltage sensing circuitor any input period sensing circuit. In addition, since the switch unitcan be simply formed, additional LED channels can be added in the samearea. In addition, since the forward voltage Vf at each LED channel canbe controlled and redistributed, the efficiency of the switch unitincreases and the combination of LEDs can be freely performed. Inaddition, since the LED operation unit is formed as the blocks, thelighting device of the present invention has distinguishable features toeasily expand lighting by using a structure in which blocks areconnected. In addition, when m LED operation units are connected inparallel, m times brightness can be used regardless of the amount of theinput voltage, compared with using one LED operation unit. In addition,when the lighting is expanded by giving different rectifier circuitcharacteristics to the rectifier circuit unit of each of the LEDoperation units, the lighting device of the present invention hasdistinguishable features to use lighting satisfied to the expanded area.

FIG. 10 is a diagram showing a structure of an LED lighting devicehaving one LED operation unit, according to some embodiment of thepresent invention.

The power source unit 10 supplies the input power. Since the powersource unit 10 uses an AC power source, the amount of the input voltageis periodically changed as time passes. The rectifier circuit unit 20receives the AC input power from the power source unit 10, rectifies theinput power, and outputs a rectified power.

The LED unit 30 receives the power from the rectifier circuit unit 20 toperform the operation. The plurality of the LED channels are connectedin series, and the resistor unit 35 is connected to a lower portion ofthe last LED channel.

Hereinafter, the present invention will be described with an assumptionof n=4 for easy description.

The switch unit 40 includes a plurality of the switches 41, 42, 43, 44,45. The n^(th) switch is connected to the rear end of the n^(th) LEDchannel to control an operation of the LED channel. The n^(th) switch iscontrolled by a sum of a current of the n^(th) switch and a current ofthe (n+1)^(th) switch, which flows through the current sensing resistor.

The current sensing resistor 50 is connected to each of the switches 41,42, 43, 44, 45 included in the switch unit 40. Thus, when currents flowthrough the switches, the current flowing through the current sensingresistor 50 is a sum of the currents flowing through the switches.

In FIG. 10, for example, the second LED channel 32 and the first switch41 are connected to an end next to the first LED channel 31. The thirdLED channel 33 and the second switch 42 are connected to an end next tothe second LED channel 32. The fourth LED channel 34 and the thirdswitch 43 are connected to an end next to the third LED channel 33. Theresistor unit 35 and the fifth switch 44 are connected to an end next tothe fourth LED channel 34. The fifth switch 45 is connected to an endnext to the resistor unit 35.

Herein, each of the switches consists of a FET (Field EffectTransistor), for example, a NMOS FET.

The current sensing resistor 50 is connected to each of the switches 41,42, 43, 44, 45 included in the switch unit 40. Thus, when currents flowthrough the switches, the current flowing through the current sensingresistor 50 is a sum of the currents flowing through the switches.

The current sensing resistor 50 may consist of a variable resistor.

According to the present invention, the LED channels operate accordingto the amount of the input power source. A corresponding LED channeloperates according to the amount of the rectified power source inputtedthe LED unit 30.

The operations of the switch unit 40, the current sensing resistor 50,and the resistor unit 35 according to this embodiment can be describedwith reference of the above description of FIG. 4.

Thus, according to the present invention, the resistor unit 35 isconnected to the last end of the LED unit 30 and the voltage isdistributed to the resistor unit 35. When a voltage equal to or greaterthan the rated voltage is inputted, the heat generated at the fifthswitch 45 is distributed to the resistor unit 35, thereby preventing thefifth switch 45 from overheating. In this way, according to the presentinvention, when the input voltage equal to or greater than the ratedvoltage is inputted, some of the overheat generated at the switch unit40 is distributed to the resistor unit 35 to be heated, thereby reducingthe overheat at the switch unit 40 formed of the IC and providing thestability of the switch unit 40.

In addition, this embodiment has the same distinguishable features ofpower consumption as those in the embodiment of FIG. 4. Accordingly, asthe forward voltage Vf of the LED channel is redistributed, the heatgeneration at the switch unit 40 becomes same even when the inputvoltage is changed.

FIG. 11 is a diagram showing a circuit structure having one or more LEDoperation units, according to some embodiment of the present invention.

According to the present invention, the LED unit 30 consists of blocks.Thus, the LED unit 30 formed as blocks is more than one and is connectedin parallel, as shown in FIG. 11, thereby forming a lighting devicehaving a LED unit formed in a parallel structure.

For this purpose, the LED lighting device having the LED unit formed asblocks of the present invention include a block connection unit having amatrix connection structure.

The LED unit 30 formed as blocks has a block structure having a certainconnection structure and may be connected to the block connection unitin a insertion manner. That is, the LED unit 30 formed as blocks of theblock connection unit is inserted and the matrix structure of the blockconnection unit is connected to have a predetermined circuit structure,thereby providing a predetermined circuit structure. For example, asshown in FIG. 11, the block connection unit is connected to have aplurality of parallel connection structures, the LED unit 30 is insertedto a corresponding position, and then the LED units 30_1, 30_2, 30_3formed as blocks have parallel connection structures.

As shown in FIG. 11, when the LED units 30_1, 30_2, 30_3 are connectedin parallel and the same input voltage is inputted, a lighting devicehaving three times brightness can be formed, compared with a lightingdevice having one LED unit 30.

In FIG. 11, the LED unit is formed as blocks and connected to the blockconnection unit, as an exemplary description. However, the LED channelmay be formed as blocks and connected to the block connection unit toform a predetermined circuit.

FIG. 12 and FIG. 13 are diagrams showing structures of LED channelshaving one or more LEDs, according to some embodiment of the presentinvention.

In FIG. 11, the circuit structure, in which the LED unit 30 is formed asblocks and one or more LED units 30 are connected in parallel, therebyincreasing the brightness of the lighting device, is described. However,each of LED channels 31, 32, 33, 34 are formed as blocks and one or moreLED channels 31, 32, 33, 34 are connected to a block connection unithaving a matrix connection structure, thereby forming a lighting devicehaving predetermined lighting brightness and a lighting colour.

For example, the LED channel 31 having four LEDs connected in series isformed as one block, as shown in FIG. 12.

Otherwise, for example, as shown in FIG. 13, the LED unit 32 may have astructure in which four LEDs connected in series is formed as one groupand the groups each having four LEDs are connected in parallel.

As the blocks having LEDs are formed, a LED block may be formedaccording to a corresponding input voltage when the input voltage is110V or 220V. That is, a LED circuit having maximum efficiency may beeasily formed according to the input voltage.

Herein, each block can be formed to have a different lighting colour.

The lighting device of the present invention described above hasadvantages as follows. The FET switches can be automatically switchedaccording to the input voltage without any input voltage sensing circuitor any input period sensing circuit. In addition, since the switch unitcan be simply formed, additional LED channels can be added in the samearea. In addition, since the forward voltage Vf at each LED channel canbe controlled and redistributed, the efficiency of the switch unitincreases and the combination of LEDs can be freely performed. Inaddition, when the plurality of the LED operation units are connected inseries, n times brightness can be used in the section in which then^(th) LED operation unit operates, compared with using one LEDoperation unit. In addition, the LED channel or the LED unit formed asblocks is connected to the block connection unit, thereby easily forminga circuit of a lighting device having predetermined lighting brightnessand a lighting colour.

FIG. 14 is a diagram showing a structure of a lighting device in whichthe heat generation at a switch unit decreases, when a voltage equal toor greater than the rated voltage is inputted, according to someembodiment of the present invention.

The lighting device, in which heating of a switch unit decreases when avoltage equal to or greater than the rated voltage is inputted, includesthe power source unit 10, the rectifier circuit unit 20, the LED unit30, the switch unit 40 and the dimming control unit 50.

The power source unit 10 supplies the input power. The rectifier circuitunit 20 receives the AC input power from the power source unit 10,rectifies the input power, and outputs a rectified power.

The LED unit 30 includes n LED channels connected in series, and theresistor unit 35 is connected to the last end of the last LED channel34.

In FIG. 14, for example, the LED unit 30 includes 4 LED channels 31, 32,33, 34. The resistor unit 35 is connected to an end next to the last LEDchannel 34 among the LED channels connected each other in series.

The switch unit 40 includes n+1 switches to operate the LED channelsaccording to the input power source. Herein, the n switches among then+1 switches controls the operations of the LED channels according tothe input power source, and the (n+1)^(th) switch operates the resistorunit 35.

In FIG. 14, for example, the second LED channel 32 and the first switch41 are connected to an end next to the first LED channel 31. The thirdLED channel 33 and the second switch 42 are connected to an end next tothe second LED channel 32. The fourth LED channel 34 and the thirdswitch 43 are connected to an end next to the third LED channel 33. Theresistor unit 35 and the fourth switch 44 are connected to an end nextto the fourth LED channel 34. The fifth switch 45 is connected to an endnext to the resistor unit 35.

Herein, each of the switches consists of a FET (Field EffectTransistor), for example, a NMOS FET.

The dimming control unit 50 may consist of a variable resistor.

The variable resistor 51 is connected to each of the switches 41, 42,43, 44, 45 included in the switch unit 40. Thus, when currents flowthrough the switches, the current flowing through the current variableresistor 51 is a sum of the currents flowing through the switches.

The dimming control unit 50 further includes a switch (not shown)controlling the resistance value of the variable resistor 51.

According to the present invention, the LED channels operate accordingto the amount of the input power source. A corresponding LED channeloperates according to the amount of the rectified power source inputtedthe LED unit 30.

The operations of the switch unit 40, the current sensing resistor 50,and the resistor unit 35 according to this embodiment can be describedwith reference of the above description of FIG. 4.

Thus, according to the present invention, the resistor unit 35 isconnected to the last end of the LED unit 30 and the voltage isdistributed to the resistor unit 35. When a voltage equal to or greaterthan the rated voltage is inputted, the heat generated at the fifthswitch 45 is distributed to the resistor unit 35, thereby preventing thefifth switch 45 from overheating. In this way, according to the presentinvention, when the input voltage equal to or greater than the ratedvoltage is inputted, some of the overheat generated at the switch unit40 is distributed to the resistor unit 35 to be heated, thereby reducingthe overheat at the switch unit 40 formed of the IC and providing thestability of the switch unit 40.

FIG. 15 is a diagram showing currents applied to the positions of LEDchannels according to input voltages, according to some embodiment ofthe present invention.

As described in FIG. 15, when a voltage equal to greater than theforward voltage Vf is inputted according to the input voltage, asaturation current flows through each of the LED channels 31, 32, 33,34.

Section a in FIG. 15 is a section in which the input voltage operatingthe first LED channel 31 is inputted. Thus, in the section a, a currentI1 flows through the first LED channel 31 and the first switch 41.

Section b is a section in which the input voltage operating the secondLED channel 32 is inputted. Thus, in the section b, a current I2 flowsthrough the second LED channel 32 and the second switch 42.

Section c is a section in which the input voltage operating the thirdLED channel 33 is inputted. Thus, in the section c, a current I3 flowsthrough the third LED channel 33 and the third switch 43.

Section d is a section in which the input voltage operating the fourthLED channel 34 is inputted. Thus, in the section d, a current I4 flowsthrough the fourth LED channel 34 and the fourth switch 44.

In FIG. 15, the section a is a section in which the first switchoperates and then the first LED channel operates. The section b is asection in which the second switch operates and then the first LEDchannel and the second LED channel operate. The section c is a sectionin which the third switch operates and then the first LED channel, thesecond LED channel, and the third LED channel operate. The section d isa section in which the fourth switch operates and then the first LEDchannel, the second LED channel, the third LED channel, and the fourthLED channel operate.

In the present invention, the methods of dimming control are two methodsas follows.

First, the dimming control is performed by controlling the resistancevalue of the variable resistor 51 included in the dimming control unit50, controlling the operation of the n^(th) and (n+1)^(th) switches, andthen controlling the operation of the n^(th) and (n+1)^(th) LEDchannels.

That is, the resistance value of the variable resistor 51 is controlledto control the number of the operations of the LED channel. Thus, theresistance value of the variable resistor 51 is controlled regardless ofthe input voltage to the sequence of the switches to be operated, andthen the number of LED channel to be operated can be controlled.

Thus, when a bright lighting is required, the variable resistor value isdecreased to make the number of the switches to be operated greater andto increase the number of the LED channels to be operated, and then thelighting becomes bright. When a weak lighting is required, the variableresistor value is increased to make the number of the switches to beoperated lower and to decrease the number of the LED channels to beoperated, and then the lighting becomes weak.

That is, the number of LEDs to be operated is controlled to perform thedimming control regardless of the section of input voltage.

Second, the dimming control is performed by controlling the resistancevalue of the variable resistor 51 included in the dimming control unit50, controlling the current value flowing through the n^(th) switch, andthen changing the current value flowing through the LED channel to beoperated through the n^(th) switch.

The dimming control by the second method will be described in FIG. 16.

FIG. 16 is a diagram showing a dimming control by changing a currentvalue flowing through an LED channel, according to some embodiment ofthe present invention.

According to the present invention, the dimming control is performed bycontrolling the resistance value of the variable resistor 51 included inthe dimming control unit 50, controlling the current value flowingthrough the n^(th) switch, and then changing the current values flowingthrough all LED channels to be operated by the n^(th) switch.

According to the present invention, when the current flowing through theLED channel to be operated through the n^(th) switch is I, theresistance value of the variable resistor 51 is changed to change thecurrent value of the current I flowing through the LED channel in therange from Ivmax to Ivmin.

That is, when a bright lighting is required, the variable resistor valueis reduced to make the operation current value of the LED channel Ivmax,thereby controlling the dimming of the LED channel bright. When a weaklighting is required, the variable resistor value is raised to make theoperation current value of the LED channel Ivmin, thereby controllingthe dimming of the LED channel dark.

In addition, the present invention has distinguishable featuresaccording to the power consumption.

From the first switch to the fourth switch, when the input voltageincreases, the n^(th) switch is operated by the remained voltage formedby subtracting the forward voltage at the n^(th) LED channel. When themore voltage is inputted, the n^(th) switch becomes the off-state andthe (n+1)^(th) switch operates so as to increase the power consumption(heat generation). However, the total power consumption is within aspecific system standard range. When a voltage equal to or greater thanthe rated voltage is inputted, an excessive current flows through thefifth switch 45 (the last switch), and then the power consumption (heatgeneration) becomes greater than the system standard range. Thus, whenthe voltage equal to or greater than the rated voltage is inputted,overheating occurs at the fifth switch 45.

According to the present invention, since the resistor unit 35 isincluded, heat can be generated at the resistor unit 35 when the voltageequal to or greater than the rated voltage is inputted, thereby reducingthe heat generating at the fifth switch 45.

In addition, according to the present invention, the forward voltages Vfof the LED channels are unevenly redistributed, and then the powerconsumed at each switch becomes almost same. That is, the forwardvoltage Vf of the (n+1)^(th) LED channel increases greater than theforward voltage Vf of the n^(th) LED channel, and then the powerconsumption at the n^(th) switch and the power consumption at the(n+1)^(th) switch become almost same. By the redistribution of theforward voltages Vf of the LED channels, the heat generation at theswitch unit 40 becomes same regardless of the change of the inputvoltage.

Herein, although the forward voltage Vf of each LED channel can befreely changed, the total amount of the forward voltages Vf is set asthe maximum value of the input voltage

The lighting device of the present invention described above hasadvantages as follows. The FET switches can be automatically switchedaccording to the input voltage without any input voltage sensing circuitor any input period sensing circuit. In addition, since the switch unitcan be simply formed, additional LED channels can be added in the samearea. In addition, since the forward voltage Vf at each LED channel canbe controlled and redistributed, the efficiency of the switch unitincreases and the combination of LEDs can be freely performed.

FIG. 17 is a diagram showing a structure of an LED lighting device inwhich a capacitor is connected in parallel to a LED channel to prevent aflicker phenomenon, according to some embodiment of the presentinvention.

The LED lighting device preventing the flicker phenomenon having thepower source unit 10, the rectifier circuit unit 20, the LED unit 30,the switch unit 40, and the current sensing resistor 50.

The power source unit 10 supplies the input power. The rectifier circuitunit 20 receives the AC input power from the power source unit 10,rectifies the input power, and outputs a rectified power.

The LED unit 30 includes n LED channels connected in series. A resistorunit 36 is connected to the last end of the last LED channel 35. Inaddition, each of the LED channels has a structure in which a capacitoris connected in parallel.

The switch unit 40 includes n+1 switches. The mth switch is connected tothe rear end of the mth LED channel and the last switch is connected tothe rear end of the resistor unit. Herein, “n” and “m” indicate naturalnumbers.

Hereinafter, the present invention will be described with an assumptionof n=4 for easy description.

In FIG. 17, for example, the second LED channel 32 and the first switch41 are connected an end next to the first LED channel 31. The third LEDchannel 33 and the second switch 42 are connected an end next to thesecond LED channel 32. The fourth LED channel 34 and the third switch 43are connected an end next to the third LED channel 33. The resistor unit35 and the fourth switch 44 are connected an end next to the fourth LEDchannel. The fifth switch 45 is connected an end next to the resistorunit 35.

Herein, each switch in the switch unit 40 consists of a FET (FieldEffect Transistor), for example, a NMOS FET.

The current sensing resistor 50 may consist of a variable resistor.

The current sensing resistor 50 is connected to each of the switches 41,42, 43, 44, 45 included in the switch unit 40. Thus, when currents flowthrough the switches, the current flowing through the current sensingresistor 50 is a sum of the currents flowing through the switches.

Before each of capacitors 36, 37, 38, 39 connected in parallel to theLED channels is fully charged, the switch unit 40 of the presentinvention operates in following manners.

The operations of the switch unit 40, the current sensing resistor 50,and the resistor unit 35 according to this embodiment can be describedwith reference of the above description of FIG. 4.

Thus, according to the present invention, the resistor unit 35 isconnected to the last end of the LED unit 30 and the voltage isdistributed to the resistor unit 35. When a voltage equal to or greaterthan the rated voltage is inputted, the heat generated at the fifthswitch 45 is distributed to the resistor unit 35, thereby preventing thefifth switch 45 from overheating. In this way, according to the presentinvention, when the input voltage equal to or greater than the ratedvoltage is inputted, some of the overheat generated at the switch unit40 is distributed to the resistor unit 35 to be heated, thereby reducingthe overheat at the switch unit 40 formed of the IC and providing thestability of the switch unit 40.

The switching method of the switch unit 40 is described above for thecase when each of capacitors 36, 37, 38, 39 connected in parallel to theLED channels is not fully charged.

When the input voltage increases and each of the capacitors 36, 37, 38,39 are fully charged, the power can be supplied to the LED channelconnected in parallel by the voltage charged in the capacitor even whenthe input voltage decreases.

That is, when the input voltage is less than 200V, the fourth LEDchannel 34 does not operate in a conventional lighting device. While,according to the present invention, a voltage charged in the fourthcapacitor 39 connected in parallel to the fourth LED channel 34 issupplied to the fourth LED channel 34, thereby operating the fourth LEDchannel 34.

In addition, when the input voltage is less than 150V, the third LEDchannel 33 does not operate in the conventional lighting device. While,according to the present invention, a voltage charged in the thirdcapacitor 38 connected in parallel to the third LED channel 33 issupplied to the third LED channel 33, thereby operating the third LEDchannel 33.

In addition, when the input voltage is less than 100V, the second LEDchannel 32 does not operate in the conventional lighting device. While,according to the present invention, a voltage charged in the secondcapacitor 37 connected in parallel to the second LED channel 32 issupplied to the second LED channel 32, thereby operating the second LEDchannel 32.

In addition, when the input voltage is less than 50V, the first LEDchannel 31 does not operate in the conventional lighting device. While,according to the present invention, a voltage charged in the firstcapacitor 36 connected in parallel to the first LED channel 31 issupplied to the first LED channel 31, thereby operating the first LEDchannel 31.

According to the present invention, when the capacitor connected inparallel to the LED panel is fully charged, a voltage charged in acapacitor can be supplied to the corresponding LED channel, therebyoperating the LED channel, even when the input voltage does not reachthe voltage operating the corresponding LED channel.

Thus, all LED channels may be operated regardless of the input voltage,thereby preventing a flicker phenomenon.

FIG. 18 is a diagram showing the operation of an LED channel accordingto an input voltage, according to some embodiment of the presentinvention.

As described above, when a voltage equal to or greater than the forwardvoltage Vf is inputted according to the input voltage, a current flowsthrough each of LED channels 31, 32, 33, 34.

In FIG. 18, “V1” indicates a voltage with which the first LED channel 31can be operated. “V2” indicates a voltage with which the second LEDchannel 32 can be operated. “V3” indicates a voltage with which thirdLED channel 33 can be operated. “V4” indicates a voltage with which thefourth LED channel 34 can be operated. “V5” indicates a voltage equal toor greater than the rated voltage.

In FIG. 18, “I1” indicates a current flowing through the first LEDchannel 31. “I2” indicates a current flowing through the second LEDchannel 32. “I3” indicates a current flowing through the third LEDchannel 33. “I4” indicates a current flowing through the fourth LEDchannel 34. “I5” indicates a current flowing through the resistor unit35 and the fifth switch 45.

Before the capacitor is not fully charged, the current according to theinput current flows through each of capacitors. However, current doesnot flow through the capacitor fully charged, but flows though the LEDchannels connected in parallel.

In the section a and the section i, the input voltage is inputtedbetween V1 and V2 and the first LED channel 31 operates. In this case,the current I1 flows through the first switch 41.

In the section b and the section h, the input voltage is inputtedbetween V2 and V3 and the second LED channel 32 operates. In this case,the current I2 flows through the second switch 42.

In the section c and the section g, the input voltage is inputtedbetween V3 and V4 and the third LED channel 33 operates. In this case,the current I3 flows through the third switch 43.

In the section d and the section f, the input voltage is inputtedbetween V4 and V5 and the fourth LED channel 34 operates. In this case,the current I4 flows through the fourth switch 44.

In the section e, the input voltage equal to or greater than the ratedvoltage is inputted, and current I5 flows through the resistor unit 35and the fifth switch 45.

In a conventional lighting device, only the first LED channel 31operates in the section a and the section i. The first LED channel 31and the second LED channel 32 operate in the section b and the sectionh. The first LED channel 31, the second LED channel 32, and the thirdLED channel 33 operate in the section c and the section g. The first LEDchannel 31, the second LED channel 32, the third LED channel 33, and thefourth LED channel 34 operate in the section d and the section f. Thus,the LED channels sequentially operates or not according to the amount ofthe input voltage, thereby generating a flicker phenomenon.

That is, conventionally, only when the input voltage reaches a cartainvoltage operating a corresponding LED channel, the corresponding LEDchannel operates. However, according to the present invention, whenvoltage is sufficiently charged in the capacitors, the capacitorconnected in parallel to the each of the LED channels supplies a voltageto the corresponding LED channel, and then all LED channels can operateregardless of the input voltage.

FIG. 19 is a diagram showing a brightness change according to an inputvoltage, according to some embodiment of the present invention.

FIG. 19(a) is a diagram showing brightness according to the inputvoltage of a conventional lighting device.

In the conventional lighting device, the LED channel to be operatedaccording to the input voltage is changed, the LED channel to beoperated according to the section of the input voltage is changed, andthen brightness is changed. That is, brightness is changed in a stepfunctional manner, as shown in FIG. 19(a).

FIG. 19(b) is a diagram showing brightness according to the inputvoltage of LED lighting device preventing a flicker phenomenon,according to the present invention.

The LED lighting device preventing the flicker phenomenon of the presentinvention receives voltage from the capacitor connected in parallel tothe LED channel, all LED channels can be operated regardless of theamount of the input voltage except the section in which the capacitor isfully charged, thereby maintaining constant brightness, as shown in FIG.19(b).

The lighting device of the present invention described above hasadvantages as follows. When a voltage equal to or greater than the ratedvoltage is inputted and an over-current flows, a current blockingcontrol unit blocks current flowing through the switch unit formed of ICand protects the switch unit. In addition, the FET switches can beautomatically switched according to the input voltage without any inputvoltage sensing circuit or any input period sensing circuit. Inaddition, since the switch unit can be simply formed, additional LEDchannels can be added in the same area. In addition, since the forwardvoltage Vf at each LED channel can be controlled and redistributed, theefficiency of the switch unit increases and the combination of LEDs canbe freely performed.

FIG. 20 is a diagram showing a structure of an LED lighting devicehaving a circuit to reduce a flicker phenomenon, according to someembodiment of the present invention.

The LED lighting device having a circuit to reduce a flicker phenomenonof the present invention includes the power source unit 10, therectifier circuit unit 20, the charge storage circuit unit 100, and theLED operation unit 200.

The power source unit 10 supplies the input power. Since the powersource unit 10 uses an AC power source, the amount of the input voltageis periodically changed as time passes. The rectifier circuit unit 20receives the AC input power from the power source unit 10, rectifies theinput power, and outputs a rectified power.

When a voltage inputted from the rectifier circuit unit 20 is a highvoltage, the charge storage circuit unit 100 stores charge. When thevoltage is a low voltage, the charge storage circuit unit 100 outputsthe stored charge to the LED operation unit 200.

The structure and function of the charge storage circuit unit 100 willbe described in detains in FIG. 21.

The LED operation unit 200 includes the LED unit 30, the switch unit 40,and the current sensing resistor 50.

The LED unit 30 includes the plurality of the LED channels (n LEDchannels) connected in series. The resistor unit 35 is connected to alower portion of the last LED channel 34.

The switch unit 40 includes n+1 switches to operate the LED channelsaccording to the input power source. Herein, the n switches among then+1 switches controls the operations of the LED channels according tothe input power source, and the (n+1)^(th) switch operates the resistorunit 35.

Hereinafter, the present invention will be described with an assumptionof n=4 for easy description.

In FIG. 20, for example, the second LED channel 32 and the first switch41 are connected to an end next to the first LED channel 31. The thirdLED channel 33 and the second switch 42 are connected to an end next tothe second LED channel 32. The fourth LED channel 34 and the thirdswitch 43 are connected to an end next to the third LED channel 33. Theresistor unit 35 and the fourth switch 44 are connected to an end nextto the fourth LED channel 34. The fifth switch 45 is connected to an endnext to the resistor unit 35.

Herein, each of the switches consists of a FET (Field EffectTransistor), for example, a NMOS FET.

The current sensing resistor 50 is connected to each of the switches 41,42, 43, 44, 45 included in the switch unit 40. Thus, when currents flowthrough the switches, the current flowing through the current sensingresistor 50 is a sum of the currents flowing through the switches.

The current sensing resistor 50 may consist of a variable resistor.

According to the present invention, the LED channels operate accordingto the amount of the input power source. A corresponding LED channeloperates according to the amount of the rectified power source inputtedthe LED unit 30.

The operations of the switch unit 40, the current sensing resistor 50,and the resistor unit 35 according to this embodiment can be describedwith reference of the above description of FIG. 4.

Thus, according to the present invention, the resistor unit 35 isconnected to the last end of the LED unit 30 and the voltage isdistributed to the resistor unit 35. When a voltage equal to or greaterthan the rated voltage is inputted, the heat generated at the fifthswitch 45 is distributed to the resistor unit 35, thereby preventing thefifth switch 45 from overheating. In this way, according to the presentinvention, when the input voltage equal to or greater than the ratedvoltage is inputted, some of the overheat generated at the switch unit40 is distributed to the resistor unit 35 to be heated, thereby reducingthe overheat at the switch unit 40 formed of the IC and providing thestability of the switch unit 40.

In addition, this embodiment has the same distinguishable features ofpower consumption as those in the embodiment of FIG. 4. Accordingly, asthe forward voltage Vf of the LED channel is redistributed, the heatgeneration at the switch unit 40 becomes same even when the inputvoltage is changed.

FIG. 21 is a diagram showing a structure and a function of a chargestorage circuit unit, according to some embodiment of the presentinvention.

The charge storage circuit unit 100 includes a first condenser 101, asecond condenser 104, a first diode 105, a second diode 103, and a thirddiode 106.

In the circuit structure of the charge storage circuit unit 100, thesecond diode 103 is connected in a forward direction between the firstcondenser 101 and the second condenser 104. An end of the firstcondenser 101 is connected to a power source voltage node of therectifier circuit unit 20. An end of the second condenser 104 isconnected to a ground. The first diode 105 is connected in a backwarddirection between the ground and a node to which the first condenser 101and the second diode 103 are connected. The third diode 106 is connectedbetween the LED unit 30 and a node to which the second condenser 104 andsecond diode 103 are connected. Herein, the resistor 102 may be furtherconnected between the second diode 103 and a node to which the firstcondenser 101 and first diode 105 are connected.

The charge storage circuit unit 100 receives a voltage from therectifier circuit unit 20 and stores charges. In addition, when thevoltage outputted from the rectifier circuit unit 20 is lower than thevoltage stored in the charge storage circuit unit 100, the storedcharges are outputted to provide power to the LED operation unit 200.

Since the stored charges are outputted to provide power to the LED unit30 of the LED operation unit 200 when the voltage outputted from therectifier circuit unit 20 is lower, the charge storage circuit unit 100supplies a voltage to an LED unit channel which does not operate whenthe voltage outputted from the rectifier circuit unit 20 is lower. Thus,when lower input voltage inputted from the power source unit 10, the LEDchannel not to be operated can be operated, thereby reducing a flickerphenomenon.

In FIG. 21, when a voltage outputted from the rectifier circuit unit 20is high, the path in which charges are stored to the charge storagecircuit unit 100 is shown as an arrow. In the charge storage circuitunit 100, when a voltage outputted from the rectifier circuit unit 20 ishigh, a current flows through the first condenser 101, the second diode103 and the second condenser 104, thereby storing charges in the firstcondenser 101 and the second condenser 104. In addition, when a voltageoutputted from the rectifier circuit unit 20 is low (that is, thevoltage lower than the voltage stored in the charge storage circuit unit100), the charges stored in the first condenser 101 and the secondcondenser 104 are outputted, thereby supplying a voltage to the LED unit30.

FIG. 22 is a diagram showing the amount of a voltage supplied to an LEDoperation unit, according to some embodiment of the present invention.

According to the present invention, the amount of the voltage inputtedin the LED operation unit 200 is changed, as shown in FIG. 22.

Herein, “V1” indicates the maximum voltage of the input voltage. “V2”indicates a voltage stored in the charge storage circuit unit 100.

For a conventional LED lighting device without the charge storagecircuit unit 100, LED channels sequentially operates or not according tothe amount of the input voltage, thereby generating a significantflicker phenomenon.

However, according to the present invention, since the charge storagecircuit unit 100 is included, a constant voltage V2 or more can besupplied to the LED unit 30, thereby reducing the flicker phenomenon,compared with the conventional LED lighting device.

For example, when the voltage V1 is a minimum voltage to operate thesecond LED channel 32, a voltage supplied to the LED unit 30 is alwaysequal to or greater than voltage V1 in the LED lighting device havingthe circuit which reduces the flicker phenomenon of the presentinvention, and then the first LED channel 31 and the second LED channel32 operates regardless of the amount of the input voltage.

That is, in the conventional LED lighting device, the first LED channel31 and the second LED channel 32 operate or not according to the amountof the input voltage in the section A, thereby generating the flickerphenomenon caused by the first LED channel 31 and the second LED channel32. However, in the present invention, all of the first LED channel 31and the second LED channel 32 operate, and then any flicker phenomenoncaused by the first LED channel 31 and the second LED channel 32 doesnot occur.

However, in the section B, a flicker phenomenon caused by the third LEDchannel 33 and the fourth LED channel 34, as the same as theconventional LED lighting device.

The lighting device of the present invention described above hasadvantages as follows. The FET switches can be automatically switchedaccording to the input voltage without any input voltage sensing circuitor any input period sensing circuit. In addition, since the switch unitcan be simply formed, additional LED channels can be added in the samearea. In addition, since the forward voltage Vf at each LED channel canbe controlled and redistributed, the efficiency of the switch unitincreases and the combination of LEDs can be freely performed. Inaddition, the charge storage circuit unit is included to supply thestored charges to the LED unit, and then a voltage is supplied to theLED channel, which does not operate at the lower voltage, to operate,thereby reducing the flicker phenomenon.

FIG. 23 is a diagram showing a structure of an LED lighting devicehaving a circuit to eliminate ripple, according to some embodiment ofthe present invention.

The LED lighting device having the circuit to eliminate ripple of thepresent invention includes the power source unit 10, the rectifiercircuit unit 20, the ripple elimination circuit unit 100, and the LEDoperation unit 200.

The power source unit 10 supplies the input power. Since the powersource unit 10 uses an AC power source, the amount of the input voltageis periodically changed as time passes. The rectifier circuit unit 20receives the AC input power from the power source unit 10, rectifies theinput power, and outputs a rectified power.

The ripple elimination circuit unit 100 stores charges when a voltageinputted from the rectifier circuit unit 20 is high. The rippleelimination circuit unit 100 outputs the stored charges to the LEDoperation unit 200 when a voltage is low. Accordingly, the voltageinputted in the LED operation unit 200 is constant voltage after theripple is removed, as shown in FIG. 24.

The LED operation unit 200 includes the LED unit 30, the switch unit 40,and the current sensing resistor 50.

The LED unit 30 includes the plurality of the LED channels (n LEDchannels) connected in series. The resistor unit 35 is connected to alower portion of the last LED channel 34.

The switch unit 40 includes n+1 switches to operate the LED channelsaccording to the input power source. Herein, the n switches among then+1 switches controls the operations of the LED channels according tothe input power source, and the (n+1)^(th) switch operates the resistorunit 35.

Hereinafter, the present invention will be described with an assumptionof n=4 for easy description.

In FIG. 23, for example, the second LED channel 32 and the first switch41 are connected to an end next to the first LED channel 31. The thirdLED channel 33 and the second switch 42 are connected to an end next tothe second LED channel 32. The fourth LED channel 34 and the thirdswitch 43 are connected to an end next to the third LED channel 33. Theresistor unit 35 and the fourth switch 44 are connected to an end nextto the fourth LED channel 34. The fifth switch 45 is connected to an endnext to the resistor unit 35.

Herein, each of the switches consists of a FET (Field EffectTransistor), for example, a NMOS FET.

The current sensing resistor 50 is connected to each of the switches 41,42, 43, 44, 45 included in the switch unit 40. Thus, when currents flowthrough the switches, the current flowing through the current sensingresistor 50 is a sum of the currents flowing through the switches.

The current sensing resistor 50 may consist of a variable resistor.

According to the present invention, the LED channels operate accordingto the amount of the input power source. A corresponding LED channeloperates according to the amount of the rectified power source inputtedthe LED unit 30.

The operations of the switch unit 40, the current sensing resistor 50,and the resistor unit 35 according to this embodiment can be describedwith reference of the above description of FIG. 4.

Thus, according to the present invention, the resistor unit 35 isconnected to the last end of the LED unit 30 and the voltage isdistributed to the resistor unit 35. When a voltage equal to or greaterthan the rated voltage is inputted, the heat generated at the fifthswitch 45 is distributed to the resistor unit 35, thereby preventing thefifth switch 45 from overheating. In this way, according to the presentinvention, when the input voltage equal to or greater than the ratedvoltage is inputted, some of the overheat generated at the switch unit40 is distributed to the resistor unit 35 to be heated, thereby reducingthe overheat at the switch unit 40 formed of the IC and providing thestability of the switch unit 40.

In addition, this embodiment has the same distinguishable features ofpower consumption as those in the embodiment of FIG. 4. Accordingly, asthe forward voltage Vf of the LED channel is redistributed, the heatgeneration at the switch unit 40 becomes same even when the inputvoltage is changed.

The operations of the switches 41, 42, 43, 44, 45 of the switch unit 40,the operations of the LED channel 31, 32, 33, 34, and the operation ofthe resistor unit 35 are performed according to the amount of the inputvoltage inputted to the LED operation unit 200.

Thus, when a constant voltage is inputted to the LED operation unit 200by the ripple elimination circuit unit 100, for example, when a voltageequal to or greater than the voltage to operate the third LED channel 33is inputted, the first LED channel 31, the second LED channel 32, andthe third LED channel 33 are always operate. The fourth LED channel 34and the resistor unit 35 operates or not according to the amount of thevoltage inputted to the LED operation unit 200.

FIG. 24 is a diagram showing a voltage inputted to an LED operation unitby a ripple elimination circuit unit, according to some embodiment ofthe present invention.

The ripple elimination circuit unit 100 includes the resistor 101 andthe condenser 102.

In the circuit structure of the ripple elimination circuit unit 100, theresistor 101 is connected between the rectifier circuit unit 20 and theLED operation unit 200, and the condenser 102 is connected between aground and a node to which the resistor 101 and the LED operation unit200 are connected. Accordingly, when the input power from the powersource unit 10 increases and is inputted, charges are stored in thecondenser 102. When the input power from the power source unit 10decreases and is inputted, charges stored in the condenser 102 areoutputted to the LED operation unit 200, thereby eliminating the ripple.

In FIG. 24, the voltage inputted in the LED operation unit 200 becomesan about constant voltage to be inputted by the charge outputted fromthe ripple elimination circuit unit 100.

Without the ripple elimination circuit unit 100, the voltage inputted inthe LED operation unit 200 is changed as time passes and show a ripple,as shown in a dotted line.

Herein, the amount of the ripple can be controlled by controlling thecapacity of the condenser 102. For example, when the condenser 102having a high capacity is used, the voltage inputted to the LEDoperation unit 200 becomes an about constant voltage.

Accordingly, the ripple elimination circuit unit 100 outputs the storedcharges when the voltage outputted from the rectifier circuit unit 20 isa low voltage and supplies power to the LED unit 30 of the LED operationunit 200, thereby supplying a voltage to the LED unit channel which doesnot operate when a low voltage is outputted from the rectifier circuitunit 20. Thus, even when an input voltage inputted from the power sourceunit 10 is a low voltage, the LED channel which does not operated can beoperated to reduce the flicker phenomenon.

FIG. 25 is a diagram showing brightness without a ripple eliminationcircuit unit, according to some embodiment of the present invention.FIG. 26 is a diagram showing brightness with a ripple eliminationcircuit unit, according to some embodiment of the present invention.

In the present invention, for the LED lighting device without the rippleelimination circuit unit 100, the input voltage is changed as timepasses, and the number of the LED channels to operate according to theamount of the input voltage, thereby changing the brightness of thelighting device according to the input voltage.

“V1” indicates a voltage with which the first LED channel 31 can beoperated. “V2” indicates a voltage with which the second LED channel 32can be operated. “V3” indicates a voltage with which third LED channel33 can be operated. “V4” indicates a voltage with which the fourth LEDchannel 34 can be operated. In the present invention, without the rippleelimination circuit unit 100, the number of the LED channels to beoperated is changed according to the amount of the input voltage. Thatis, the brightness of the LED lighting device without the rippleelimination circuit unit 100 is changed, as shown in the hatching areas.When the input voltage is V4, the area of the brightness is greatest andthus the brightest lighting is provided. When the input voltage ischanges in a manner of V4→V3→V2→V1 with ripples, the brightnessdecreases.

In the present invention, when the LED lighting device has the rippleelimination circuit unit 100, a constant input voltage without ripplesis inputted to the LED operation unit 200, as shown in FIG. 26, and thenthe brightness corresponding to the hatching area can be provided.

In FIG. 26, the voltage inputted in the LED operation unit 200 isassumed to be equal to or greater than V4, all LED channels alwaysoperates to provide a constant brightness.

In the present invention, the effects of having the ripple eliminationcircuit unit 100 are as follows.

In a conventional LED lighting device without the ripple eliminationcircuit unit 100, the LED channels sequentially operates or notaccording to the amount of the input voltage, thereby generating asignificant flicker phenomenon.

However, in the present invention, since the ripple elimination circuitunit 100 is included, at least constant voltage is provided to the LEDunit 30, thereby reducing the flicker phenomenon, compared with theconventional LED lighting device.

The lighting device of the present invention described above hasadvantages as follows. The FET switches can be automatically switchedaccording to the input voltage without any input voltage sensing circuitor any input period sensing circuit. In addition, since the switch unitcan be simply formed, additional LED channels can be added in the samearea. In addition, since the forward voltage Vf at each LED channel canbe controlled and redistributed, the efficiency of the switch unitincreases and the combination of LEDs can be freely performed. Inaddition, since the ripple elimination circuit unit is included, thestored charge is supplied to the LED unit and at least constant voltageis always supplied to the LED channel, and then the LED channel to beoperated at the corresponding voltage operates, thereby reducing theflicker phenomenon.

FIG. 27 is a diagram showing a structure of an LED lighting deviceprotecting a switch unit by current control, according to someembodiment of the present invention.

The LED lighting device protecting a switch unit by current control ofthe present invention includes the power source unit 10, the rectifiercircuit unit 20, the LED unit 30, the switch unit 40, the currentsensing resistor 50, and the current control unit 60.

The power source unit 10 supplies the input power. The rectifier circuitunit 20 receives the AC input power from the power source unit 10,rectifies the input power, and outputs a rectified power.

The LED unit 30 includes n LED channels connected in series. Theresistor unit 35 is connected to a lower portion of the last LED channel34.

Hereinafter, the present invention will be described with an assumptionof n=4 for easy description.

In FIG. 27, the LED unit 30 includes 4 LED channels 31, 32, 33, 34. Theresistor unit 35 is connected to an end next to the last LED channel 34among the LED channels connected each other in series.

The switch unit 40 includes 5 switches to operate the LED channelsaccording to the input power source. Herein, 4 switches, the firstthrough fourth switches, among the 5 switches controls the operations ofthe LED channels according to the input power source, and the fifthswitch operates the resistor unit 35.

In FIG. 27, for example, the second LED channel 32 and the first switch41 are connected to an end next to the first LED channel 31. The thirdLED channel 33 and the second switch 42 are connected to an end next tothe second LED channel 32. The fourth LED channel 34 and the thirdswitch 43 are connected to an end next to the third LED channel 33. Theresistor unit 35 and the fourth switch 44 are connected to an end nextto the fourth LED channel 34. The fifth switch 45 is connected to an endnext to the resistor unit 35.

Herein, each of the switches consists of a FET (Field EffectTransistor), for example, a NMOS FET.

The current sensing resistor 50 may consist of a variable resistor.

The current sensing resistor 50 is connected to each of the switches 41,42, 43, 44, 45 included in the switch unit 40. Thus, when currents flowthrough the switches, the current flowing through the current sensingresistor 50 is a sum of the currents flowing through the switches.

The operations of the switch unit 40, the current sensing resistor 50,and the resistor unit 35 according to this embodiment can be describedwith reference of the above description of FIG. 4.

Thus, according to the present invention, the resistor unit 35 isconnected to the last end of the LED unit 30 and the voltage isdistributed to the resistor unit 35. When a voltage equal to or greaterthan the rated voltage is inputted, the heat generated at the fifthswitch 45 is distributed to the resistor unit 35, thereby preventing thefifth switch 45 from overheating. In this way, according to the presentinvention, when the input voltage equal to or greater than the ratedvoltage is inputted, some of the overheat generated at the switch unit40 is distributed to the resistor unit 35 to be heated, thereby reducingthe overheat at the switch unit 40 formed of the IC and providing thestability of the switch unit 40.

The current control unit 60 includes a temperature sensor.

The current control unit 60 measures temperature of the switch unit 40by using a temperature sensor and controls the current flowing throughthe switch unit 40 according to the measured temperature of the switchunit 40.

In addition, the current control unit 60 may have a memory device, anormal operation temperature range for the switch unit 40 may be set.

The current control unit 60 measures temperature of the switch unit 40by using the temperature sensor and controls the switches 41, 42, 43,44, 45 of the switch unit 40 to control the current flowing through theswitch unit 40 when the measured temperature of the switch unit 40 isdeviated from the normal operation temperature range.

For example, when the normal operation temperature range set the currentcontrol unit 60 is from 0° C. to 80° C. and the measured temperature ofthe switch unit 40 is 85° C., the measured temperature of the switchunit 40 is deviated from the normal operation temperature range. In thiscase, the current control unit 60 changes a switch performing theoperation (that is, current flows through the switch) among the switches41, 42, 43, 44, 45 of the switch unit 40 to the off-state, and thuscurrent does not flows through the switch unit 40.

FIG. 28 is a diagram showing currents applied to the positions of LEDchannels according to an input voltage, according to some embodiment ofthe present invention.

As described in FIG. 28, when a voltage equal to greater than theforward voltage Vf is inputted according to the input voltage, asaturation current flows through each of the LED channels 31, 32, 33,34.

Section a in FIG. 28 is a section in which the input voltage operatingthe first LED channel 31 is inputted. Thus, in the section a, a currentI1 flows through the first LED channel 31 and the first switch 41.

Section b is a section in which the input voltage operating the secondLED channel 32 is inputted. Thus, in the section b, a current I2 flowsthrough the second LED channel 32 and the second switch 42.

Section c is a section in which the input voltage operating the thirdLED channel 33 is inputted. Thus, in the section c, a current I3 flowsthrough the third LED channel 33 and the third switch 43.

Section d is a section in which the input voltage operating the fourthLED channel 34 is inputted. Thus, in the section d, a current I4 flowsthrough the fourth LED channel 34 and the fourth switch 44.

In FIG. 28, the section a is a section in which the first switchoperates and then the first LED channel operates. The section b is asection in which the second switch operates and then the first LEDchannel and the second LED channel operate. The section c is a sectionin which the third switch operates and then the first LED channel, thesecond LED channel, and the third LED channel, operate. The section d isa section in which the fourth switch operates and then the first LEDchannel, the second LED channel, the third LED channel, and the fourthLED channel operate.

Herein, I4 is a current flowing through the switch control unit 40 whenthe input voltage to be inputted is almost 100% of the rated voltage.That is, a current flows through the fourth switch 44.

Herein, when the input voltage greater than the rated voltage isinputted (that is, greater than 100% of the rated voltage), the currentI5 flows through the fifth switch 45.

In FIG. 28, the input voltage equal to or less than 100% of the ratedvoltage is inputted, the current flowing through the LED unit 30 and theswitch control unit 40 is changed in a step functional manner accordingthe input voltage, as shown in FIG. 28.

FIG. 29 is a diagram showing temperature control of a switch controlunit by controlling a current of a switch unit, according to someembodiment of the present invention.

The dotted lines of semicircles in the lower portion in FIG. 29indicates the input voltage, and the solid lines in a step functionalmanner indicates the current of the switch unit 40 according to theinput voltage.

In FIG. 28, since the LED channel to be operated is changed according tothe section of the input voltage, as described above, the switchoperating the LED channel is changed.

Except a voltage section in which the input voltage does not operate thefirst LED channel, currents always flow through the switch unit 40, andthen the temperature in the switch unit 40 increases as time passes forinputting the input voltage passes.

However, when the temperature of the switch unit 40 continuouslyincreases to reach a certain temperature, the switch unit 40 may bedamaged or perform a malfunction due to heating.

Thus, according to the present invention, the temperature of the switchunit 40 is measured and the current flowing through the switch unit 40is blocked to decrease the temperature of the switch unit 40 when themeasured temperature is greater than normal operation temperature.

The method of decreasing the temperature by blocking the current, whichflows through the switch unit 40 according to the temperature of theswitch unit 40 with reference to FIG. 29 will be described.

First, the normal operation temperature of the switch unit is equal toor less than T2, and a malfunction temperature in which the switch unitmalfunctions is T1. In addition, the malfunction temperature T1 is setin the current control unit 60.

When the input voltage is inputted in the LED unit 30 and a currentflows through the switch unit 40, the temperature of the switch unit 40increases, as shown in FIG. 29.

When the temperature of the switch unit 40 increases to be greater thanthe normal operation temperature T2 and reach the malfunctiontemperature T1, the current control unit 60 controls the switchesthrough which a current flows among the switch control unit 40 to blockthe current. Then, when the temperature of the switch control unit 40decreases to be lower than the normal operation temperature T2, thecurrent control unit 60 controls a switch corresponding to the amount ofthe input voltage and makes a current flow, thereby operating a LEDchannel corresponding to the amount of the input voltage. Then, when thetemperature of the switch unit 40 increases to be greater than thenormal operation temperature T2 and reach the malfunction temperatureT1, the current control unit 60 controls again the switches throughwhich the current flows among the switch control unit 40 to block thecurrent. Then, when the temperature of the switch control unit 40decreases to be lower than the normal operation temperature T2, thecurrent control unit 60 operates again a LED channel corresponding tothe amount of the input voltage.

The operation of the current control unit 60 will be described withreference to FIG. 29.

When the input voltage is inputted and the temperature of the switchcontrol unit 40 increases to reach the malfunction temperature T1 at atime 1, the current control unit 60 controls the third switch 43 throughwhich a current I3 flows to block the current I3. Then, when thetemperature of the switch control unit 40 decreases to reach the normaloperation temperature T2 at a time 2, the current control unit 60controls the first switch 41 corresponding to the input voltage to flowa current I1.

Then, when the temperature of the switch control unit 40 increases toreach the malfunction temperature T1 at a time 3, the current controlunit 60 controls the first switch 41 to block the current I1. Then, whenthe temperature of the switch control unit 40 decreases to reach thenormal operation temperature T2 at a time 4, the current control unit 60controls the third switch 43 corresponding to the input voltage to flowa current I3.

Then, when the temperature of the switch control unit 40 increases toreach the malfunction temperature T1 at a time 5, the current controlunit 60 controls the fourth switch 44 to block the current I4. Then,when the temperature of the switch control unit 40 decreases to reachthe normal operation temperature T2 at a time 6, the current controlunit 60 controls a switch corresponding to the input voltage to flow acorresponding current.

In addition, the present invention has distinguishable featuresaccording to the power consumption.

From the first switch to the fourth switch, when the input voltageincreases, the n^(th) switch is operated by the remained voltage formedby subtracting the forward voltage at the n^(th) LED channel. When themore voltage is inputted, the n^(th) switch becomes the off-state andthe (n+1)^(th) switch operates so as to increase the power consumption(heat generation). However, the total power consumption is within aspecific system standard range. When a voltage equal to or greater thanthe rated voltage is inputted, an excessive current flows through thefifth switch 45 (the last switch), and then the power consumption (heatgeneration) becomes greater than the system standard range. Thus, whenthe voltage equal to or greater than the rated voltage is inputted,overheating occurs at the fifth switch 45.

According to the present invention, since the resistor unit 35 isincluded, heat can be generated at the resistor unit 35 when the voltageequal to or greater than the rated voltage is inputted, thereby reducingthe heat generating at the fifth switch 45.

In addition, according to the present invention, the forward voltages Vfof the LED channels are unevenly redistributed, and then the powerconsumed at each switch becomes almost same. That is, the forwardvoltage Vf of the (n+1)^(th) LED channel increases greater than theforward voltage Vf of the n^(th) LED channel, and then the powerconsumption at the n^(th) switch and the power consumption at the(n+1)^(th) switch become almost same. By the redistribution of theforward voltages Vf of the LED channels, the heat generation at theswitch unit 40 becomes same regardless of the change of the inputvoltage.

Herein, although the forward voltage Vf of each LED channel can befreely changed, the total amount of the forward voltages Vf is set asthe maximum value of the input voltage.

The lighting device of the present invention described above hasadvantages as follows. A temperature sensor is included to measure thetemperature of the switch unit formed of IC and to control the currentflowing through the switch unit, thereby maintaining the temperatureless than the malfunction temperature and protecting the switch unit.The FET switches can be automatically switched according to the inputvoltage without any input voltage sensing circuit or any input periodsensing circuit. In addition, since the switch unit can be simplyformed, additional LED channels can be added in the same area. Inaddition, since the forward voltage Vf at each LED channel can becontrolled and redistributed, the efficiency of the switch unitincreases and the combination of LEDs can be freely performed.

FIG. 30 is a diagram showing a structure of a LED lighting deviceprotecting a switch unit by controlling a current of the switch unit,according to some embodiment of the present invention.

The LED lighting device protecting the switch unit by controlling acurrent of the present invention includes the power source unit 10, therectifier circuit unit 20, the LED unit 30, the switch unit 40, thecurrent sensing resistor 50, and the switch current blocking unit 60.

The power source unit 10 supplies the input power. The rectifier circuitunit 20 receives the AC input power from the power source unit 10,rectifies the input power, and outputs a rectified power.

The LED unit 30 includes n+1 LED channels connected in series. Theresistor unit 36 is connected to the last end of the last LED channel35.

Hereinafter, the present invention will be described with an assumptionof n=4 for easy description.

In FIG. 30, the LED unit 30 includes 5 LED channels 31, 32, 33, 34, 35.The resistor unit 36 is connected in series to an end next to the lastLED channel 35 among the LED channels connected each other in series.

The switch unit 40 includes 4 switches to operate the LED channelsaccording to the input power source. Herein, the 4 switches, the firstthrough fourth switches, controls the operations of the LED channelsaccording to the input power source.

That is, the first switch 41 is connected to the first LED channel 31and turns on to operate the first LED channel 31. The second switch 42is connected to the second LED channel 32 and turns on to operate thefirst LED channel 31 and the second LED channel 32. The third switch 43is connected to the third LED channel 33 and turns on to operate thefirst LED channel 31, the second LED channel 32, and third LED channel33. The fourth switch 44 is connected to the fourth LED channel 34 andturns on to operate the first LED channel 31, the second LED channel 32,and third LED channel 33, and the fourth LED channel 34.

Herein, the last LED channel (that is, the fifth LED channel 35) isconnected to the switch current blocking unit 60 through the resistorunit 36.

The switching operation of the switching circuit unit 40 will bedescribed with reference to FIG. 30.

The second LED channel 32 and the first switch 41 are connected an endnext to the first LED channel 31. The third LED channel 33 and thesecond switch 42 are connected an end next to the second LED channel 32.The fourth LED channel 34 and the third switch 43 are connected an endnext to the third LED channel 33. The fifth LED channel 35 is connectedan end next to the fourth LED channel 34. The resistor unit 36 isconnected an end next to the fifth LED channel 35.

Herein, each switch in the switch unit 40 consists of a FET (FieldEffect Transistor), for example, a NMOS FET.

The current sensing resistor 50 may consist of a variable resistor.

The current sensing resistor 50 is connected to each of the switches 41,42, 43, 44 included in the switch unit 40. Thus, when currents flowthrough the switches, the amount of the current flowing through thecurrent sensing resistor 50 is a sum of the currents flowing through theswitches.

The operation of the switch unit 40 according to the present inventionwill be described.

Initially, the operation voltage is inputted to gates of all switches41, 42, 43, 44 to operate each of the switch (that is, the currentflows).

Herein, an operation voltage of the first switch 41 is Vgs1, anoperation voltage of the second switch 42 is Vgs2, an operation voltageof the third switch 43 is Vgs3, and an operation voltage of the fourthswitch 44 is Vgs4.

Herein, the condition of Vgs1<Vgs2<Vgs3<Vgs4 is satisfied.

Each of Vgs1, Vgs2, Vgs3, and Vgs4 is connected to the current sensingresistor 50 and affected by a voltage applied to the current sensingresistor 50.

Afterward, the switches in the switch unit 40 are automaticallycontrolled by the voltage value applied to the current sensing resistor50 according to the amount of the rectified voltage inputted in the LEDunit 30, thereby operating the LED channels.

In the present invention, a switching condition means that when currentflows two adjacent switches, a voltage is generated at the currentsensing resistor by a sum of the currents flowing through the twoadjacent switches, the operation voltage decreases due to the voltageapplied to the current sensing resistor, and then any switch having alower operation voltage first turns off.

Afterward, the switches in the switch unit 40 are automaticallycontrolled by the voltage value applied to the current sensing resistor50 according to the amount of the rectified voltage rectified at therectifier circuit unit 20 and inputted in the LED unit 30, therebyoperating the LED channels.

According to the present invention, for example, the current sensingresistor 50 is set for 10 ohm.

Table 3 shows saturation current values at the switches (FETs) andvoltages applied to the current sensing resistor when the saturationcurrent flows through switches.

Herein, “Id” indicates a saturation current of the corresponding switch.It indicates a saturation voltage when the switch operates and a currentflows. “Vrs” indicates a voltage applied to the current sensingresistor.

TABLE 3 Id (mA) Vrs First FET 20 0.2 Second FET 40 0.4 Third FET 60 0.6Fourth FET 80 0.8

In addition, a forward voltage Vf of each LED channel is 50V.

In this case, when an input voltage increases to reach about 50V, thefirst LED channel 31 begins to operate and a current I1 begins to flowthrough the first switch 41. When the input voltage is equal to orgreater than 50V, a saturation current of 20 mA flows through the firstswitch 41 and the voltage applied to the current sensing resistor 50becomes 0.2V.

When the input voltage increases to reach about 100V, the second LEDchannel 32 begins to operate and the current I2 gradually flows throughthe second switch 42. A current flowing through the current sensingresistor 50 is a sum of the currents flowing through the first switch 41of 20 mA and the current I2 flowing through the second switch 42. Thus,the voltage at the current sensing resistor 50 gradually increases. Asthe voltage applied to the current sensing resistor 50 increases, thevoltage Vgs1 inputted to the gate of the first switch 41 becomesrelatively lower, and thus the first switch 41 gets into the switchingcondition in which an on-state changes to an off-state. When the inputvoltage gradually increases to gradually increase the current I2 flowingthrough the second switch 42, the voltage applied to the current sensingresistor 50 gradually increases to relatively lower the voltage value ofVgs1, and thus the first switch 41 becomes the off-state.

When the input voltage is equal to or greater than 100V, a saturationcurrent of 40 mA flows through the second switch 42 and the first switch41 is completely the off-state.

When the input voltage increases to reach about 150V, the third LEDchannel 33 begins to operate, a current I3 gradually flows through thethird switch 43. Herein, a current flowing through the current sensingresistor 50 is a sum of the currents flowing through the second switch42 of 40 mA and the current I3 flowing through the third switch 43.Thus, the voltage applied to the current sensing resistor 50 graduallyincreases. As the voltage applied to the current sensing resistor 50increases, a voltage Vgs2 inputted to the gate of the second switch 42becomes relatively lower, and thus the second switch 42 gets into theswitching condition in which an on-state changes to an off-state. Whenthe voltage value applied to the current sensing resistor 50 graduallyincreases to relatively lower the voltage value of Vgs2, and thus thesecond switch 42 becomes the off-state.

When the input voltage is equal to or greater than 150V, a saturationcurrent of 60 mA flows through the third switch 43, and the secondswitch 42 becomes completely the off-state.

As described above, when a current sequentially flows through a(m+1)^(th), switch according to the input voltage, a mth switch becomesthe off-state.

When the input voltage increases to reach about 200V, the fourth LEDchannel 34 begins to operate, and the current I3 and the current I4gradually flow through the third switch 43 and the fourth switch 44,respectively. Herein, a current flowing through the current sensingresistor 50 is a sum of the currents flowing through the third switch 43of 60 mA and the currents flowing through the fourth switch 44 and thefifth switch 45. Likewise, when the input voltage is equal to or greaterthan 200V, a saturation current of 80 mA flows through the fourth switch44, and the third switch 43 becomes completely the off-state.

Herein, when the rated voltage is 200V and the input voltage equal to orgreater than the rated voltage is inputted, an over-current, which isgreater than the current for the switch to perform the normal operation,flows through the fourth switch 44 to flow a excessive current throughthe switch, thereby generating a significant amount of heat at theswitch. When the significant amount of heat is generated at the fourthswitch 44, the switch unit 40 formed of a IC with a FET may besignificantly damaged.

Thus, in the present invention, the fifth LED channel 35 and theresistor unit 36 are connected in series to an end next to the fourthLED channel 34. When the input voltage equal to or greater than therated voltage is inputted, a current flows through the fifth LED channel35 to the resistor unit 36, and then heat generated at the switch unit40, when a voltage equal to or greater than the rated voltage inputted,is distributed to the resistor unit 36, thereby preventing thegeneration of excessive heat at the switch unit 40.

That is, according to the present invention, when the resistor unit 36is connected to the last end of the LED unit 30, the voltage isdistributed at the resistor unit 36 and a voltage equal to or greaterthan the rated voltage is inputted, the heat generated at the fourthswitch 44 is distributed to the resistor unit 36, thereby preventing thefourth switch 44 from overheating. In this way, according to the presentinvention, when the input voltage equal to or greater than the ratedvoltage is inputted, the switch unit 40 is not overheated, therebyproviding the stability of the switch unit 40 formed of the IC.

In addition, in the present invention, in order to prevent damage of theswitch unit 40 by inputting the over-current to the switch unit 40 whena voltage equal to or greater than the rated voltage, and in order toprevent damages by the heating caused by continuous inputting thevoltage equal to or greater than the rated voltage and caused bycontinuous inputting the over-current to the switch unit 40, the switchcurrent blocking unit 60, which blocks the current flowing through theswitch unit 40, is positioned outside of the switch unit 40.

The switch current blocking unit 60 senses the current flowing throughthe fifth LED channel 35 and the resistor unit 36, and controls theswitch current blocking switch 45 positioned in the switch unit 40, whenan over-current flows, to make the switch off, thereby blocking thecurrent, which flows through the switch unit 40.

Herein, the switch current blocking unit 60 directly controls the fourthswitch 44 through which the current flows in the switch unit 40 to turnthe fourth switch 44 off and not to flow the current through the switchunit 40.

An over-current usually occurs at the last switch, that is, the fourthswitch 44, but an over-current may occur at the first through the thirdswitches caused by other reasons. The switch current blocking unit 60may control all switches in the switch unit 40, and then block thecurrent flowing through the switch unit 40 when an over-current flowsthrough the switch unit 40.

for this purpose, a stable operation current value with which the switchunit 40 is stably operated is set in the switch current blocking unit60. The switch current blocking unit 60 senses the current, compares itwith the stable operation current value, and blocks the switch throughwhich the current flows among the switches in the switch unit 40 when anover-current equal to or greater than the stable operation current valueflows, to connect the internal switch between the resistor unit 35 and aground voltage, thereby blocking the current, which flows through theswitch unit 40.

For example, when the stable operation current value set in the switchcurrent blocking unit 60 is 110 mA, a voltage equal to or greater thanthe rated voltage is inputted, and a current of equal to or greater than110 mA flows through the switch current blocking unit 60, the switchcurrent blocking unit 60 immediately turns off the switch through whichthe current flows in the switch unit 40, thereby blocking the current,which flows through the switch unit 40.

FIG. 31 is a diagram showing currents applied to the positions of LEDchannels according to an input voltage, according to some embodiment ofthe present invention.

As described above, when voltage equal to or greater than the forwardvoltage Vf inputted to each of LED channels 31, 32, 33, 34 according tothe input voltage, current flows.

In FIG. 31, “V1” indicates the maximum voltage within the rated voltage.

In FIG. 31, “I1” indicates a current flowing through the first LEDchannel 31. “I2” indicates a current flowing through the second LEDchannel 32. “I3” indicates a current flowing through the third LEDchannel 33. “I4” indicates a current flowing through the fourth LEDchannel 34.

As described above, when the input voltage is inputted within the ratedvoltage, the current flowing through the LED unit 30 is changed in thesequence of I1→I2→I3→I4→I1.

However, a voltage equal to or greater than the rated voltage isinputted, the fifth LED channel 35 operates to flow the current I5through the LED unit 30.

In FIG. 31, “V2” indicates the maximum value of the voltage equal to orgreater than the rated voltage. Section A is a section in which thevoltage equal to or greater than the rated voltage is inputted.

That is, in the section A in which the input voltage equal to or greaterthan the rated voltage us inputted, the fifth LED channel 35 operates toflow the current through the resistor unit 36, and then the heatgenerated at the switch unit 40 is distributed, thereby preventingexcessive heat generation at the switch unit 40.

FIG. 32 is a diagram showing the blockage of a current flowing through aswitch unit, when an input voltage equal to or greater than the ratedvoltage is inputted, according to some embodiment of the presentinvention.

As described above, the switch current blocking unit 60 includes thestable operation current value, senses the current flowing through LEDunit when a voltage equal to or greater than the rated voltage inputted,compares it with the stable operation current value, and then blocks thecurrent flowing through the switch unit 40 when the current is greaterthan the stable operation current value.

In FIG. 32, the section A is a section in which a voltage equal to orgreater than the rated voltage inputted. Herein, when the currentflowing through the LED unit 30 and sensed the switch current blockingunit 60 is greater than the stable operation current value, the switchcurrent blocking unit 60 controls the switch in the switch unit 40 toblock the current flowing. In addition, when the input voltage isinputted within the rated voltage and the current flowing through theLED unit 30 is less than the stable operation current value, the switchcurrent blocking unit 60 makes the last switch (that is, the fourthswitch 44) from the off-state to the on-state, thereby flowing thecurrent through the switch unit 40.

Thus, when the current flowing through the LED unit 30 and sensed by theswitch current blocking unit 60 in the section A is greater than thestable operation current value, the current flows in switch unit 30 inonly the hatching area shown in FIG. 32.

That is, in the section A in which the rated voltage damaging the switchunit 40 is inputted, a current does not flow through the switch unit 40.

In addition, the present invention has distinguishable featuresaccording to the power consumption.

From the first switch to the fourth switch, when the input voltageincreases, the n^(th) switch is operated by the remained voltage formedby subtracting the forward voltage at the n^(th) LED channel. When themore voltage is inputted, the n^(th) switch becomes the off-state andthe (n+1)^(th) switch operates so as to increase the power consumption(heat generation). However, the total power consumption is within aspecific system standard range.

In addition, according to the present invention, the forward voltages Vfof the LED channels are unevenly redistributed, and then the powerconsumed at each switch becomes almost same. That is, the forwardvoltage Vf of the (m+1)^(th) LED channel increases greater than theforward voltage Vf of the mth LED channel, and then the powerconsumption at the mth switch and the power consumption at the(m+1)^(th) switch become almost same. By the redistribution of theforward voltages Vf of the LED channels, the heat generation at theswitch unit 40 becomes same regardless of the change of the inputvoltage.

Herein, although the forward voltage Vf of each LED channel can befreely changed, the total amount of the forward voltages Vf is set asthe maximum value of the input voltage.

The lighting device of the present invention described above hasadvantages as follows. Since the switch current blocking unit isincluded, when a voltage equal to or greater than the rated voltage isinputted to flow an over-current through the switch unit formed of IC,the current flowing through the switch unit is blocked, therebyprotecting the switch unit. In addition, the FET switches can beautomatically switched according to the input voltage without any inputvoltage sensing circuit or any input period sensing circuit. Inaddition, since the switch unit can be simply formed, additional LEDchannels can be added in the same area. In addition, since the forwardvoltage Vf at each LED channel can be controlled and redistributed, theefficiency of the switch unit increases and the combination of LEDs canbe freely performed.

FIG. 33 is a diagram showing a structure of a LED lighting deviceprotecting a switch unit by controlling a current, according to someembodiment of the present invention.

The LED lighting device protecting the switch unit through the currentcontrol of the present invention includes the power source unit 10, therectifier circuit unit 20, the LED unit 30, the switch unit 40, thecurrent sensing resistor 50, and current conversion switch 60.

The power source unit 10 supplies the input power. The rectifier circuitunit 20 receives the AC input power from the power source unit 10,rectifies the input power, and outputs a rectified power.

The LED unit 30 includes n LED channels connected in series. Theresistor unit 36 is connected to the last end of the last LED channel35.

Hereinafter, the present invention will be described with an assumptionof n=4 for easy description.

In FIG. 33, the LED unit 30 includes 4 LED channels 31, 32, 33, 34. Theresistor unit 35 is connected in series to an end next to the last LEDchannel 347 among the LED channels connected each other in series.

The current conversion switch 60 is connected between the resistor unit35 and the last switch of the switch unit 40. In addition, the currentconversion switch 60 is connected to a ground voltage to change thedirection of the current according to the operation of the internalswitch.

The switch unit 40 includes 4 switches to operate the LED channelsaccording to the input power source. Herein, the 4 switches, the firstthrough fourth switches, controls the operations of the LED channelsaccording to the input power source.

That is, the first switch 41 is connected to the first LED channel 31and turns on to operate the first LED channel 31. The second switch 42is connected to the second LED channel 32 and turns on to operate thefirst LED channel 31 and the second LED channel 32. The third switch 43is connected to the third LED channel 33 and turns on to operate thefirst LED channel 31, the second LED channel 32, and third LED channel33.

The fourth switch 44 is connected to the fourth LED channel 34 throughthe resistor unit 35 and the current conversion switch 60 and turns onto operate the first LED channel 31, the second LED channel 32, andthird LED channel 33, and the fourth LED channel 34. (Note that theswitch of the current conversion switch 60 is connected to the fourthswitch 44 of switch unit 60.)

The switching operation of the switching circuit unit 40 will bedescribed with reference to FIG. 33.

The second LED channel 32 and the first switch 41 are connected an endnext to the first LED channel 31. The third LED channel 33 and thesecond switch 42 are connected an end next to the second LED channel 32.The fourth LED channel 34 and the third switch 43 are connected an endnext to the third LED channel 33. The fourth switch 44 is connected tothe fourth LED channel 34 though the resistor unit 35 and the currentconversion switch 60.

Herein, each switch in the switch unit 40 consists of a FET (FieldEffect Transistor), for example, a NMOS FET.

The current sensing resistor 50 may consist of a variable resistor.

The current sensing resistor 50 is connected to each of the switches 41,42, 43, 44 included in the switch unit 40. Thus, when currents flowthrough the switches, the amount of the current flowing through thecurrent sensing resistor 50 is a sum of the currents flowing through theswitches.

The operation of the switch unit 40 according to the present inventionwill be described.

Initially, an operation voltage is inputted to gates of all switches 41,42, 43, 44 to operate each switch (that is, the current flows).

Herein, an operation voltage of the first switch 41 is Vgs1, anoperation voltage of the second switch 42 is Vgs2, an operation voltageof the third switch 43 is Vgs3, and an operation voltage of the fourthswitch 44 is Vgs4.

Herein, the condition of Vgs1<Vgs2<Vgs3<Vgs4 is satisfied.

Each of Vgs1, Vgs2, Vgs3, and Vgs4 is connected to the current sensingresistor 50 and affected by a voltage applied to the current sensingresistor 50.

Afterward, the switches in the switch unit 40 are automaticallycontrolled by the voltage value applied to the current sensing resistor50 according to the amount of the rectified voltage inputted in the LEDunit 30, thereby operating the LED channels.

In the present invention, a switching condition means that when currentflows two adjacent switches, a voltage is generated at the currentsensing resistor by a sum of the currents flowing through the twoadjacent switches, the operation voltage decreases due to the voltageapplied to the current sensing resistor, and then any switch having alower operation voltage first turns off.

Afterward, the switches in the switch unit 40 are automaticallycontrolled by the voltage value applied to the current sensing resistor50 according to the amount of the rectified voltage rectified at therectifier circuit unit 20 and inputted in the LED unit 30, therebyoperating the LED channels.

According to the present invention, for example, the current sensingresistor 50 is set for 10 ohm.

Table 4 shows saturation current values at the switches (FETs) andvoltages applied to the current sensing resistor when the saturationcurrent flows through switches.

Herein, “Id” indicates a saturation current of the corresponding switch.It indicates a saturation voltage when the switch operates and a currentflows. “Vrs” indicates a voltage applied to the current sensingresistor.

TABLE 4 Id (mA) Vrs First FET 20 0.2 Second FET 40 0.4 Third FET 60 0.6Fourth FET 80 0.8

In addition, a forward voltage Vf of each LED channel is 50V.

In this case, when an input voltage increases to reach about 50V, thefirst LED channel 31 begins to operate and a current I1 begins to flowthrough the first switch 41. When the input voltage is equal to orgreater than 50V, a saturation current of 20 mA flows through the firstswitch 41 and the voltage applied to the current sensing resistor 50becomes 0.2V.

When the input voltage increases to reach about 100V, the second LEDchannel 32 begins to operate and the current I2 begins to flow throughthe second switch 42. A current flowing through the current sensingresistor 50 is a sum of the currents flowing through the first switch 41of 20 mA and the current I2 flowing through the second switch 42. Thus,the voltage at the current sensing resistor 50 gradually increases. Asthe voltage applied to the current sensing resistor 50 increases, thevoltage Vgs1 inputted to the gate of the first switch 41 becomesrelatively lower, and thus the first switch 41 gets into the switchingcondition in which an on-state changes to an off-state. When the inputvoltage gradually increases to gradually increase the current I2 flowingthrough the second switch 42, the voltage applied to the current sensingresistor 50 gradually increases to relatively lower the voltage value ofVgs1, and thus the first switch 41 becomes the off-state.

When the input voltage is equal to or greater than 100V, a saturationcurrent of 40 mA flows through the second switch 42 and the first switch41 is completely the off-state.

When the input voltage increases to reach about 150V, the third LEDchannel 33 operates, a current I3 gradually flows through the thirdswitch 43. Herein, a current flowing through the current sensingresistor 50 is a sum of the currents flowing through the second switch42 of 40 mA and the current I3 flowing through the third switch 43.Thus, the voltage applied to the current sensing resistor 50 graduallyincreases. As the voltage applied to the current sensing resistor 50increases, a voltage Vgs2 inputted to the gate of the second switch 42becomes relatively lower, and thus the second switch 42 gets into theswitching condition in which an on-state changes to an off-state. Whenthe voltage value inputted to the current sensing resistor 50 graduallyincreases to relatively lower the voltage value of Vgs2, and thus thesecond switch 42 becomes the off-state.

When the input voltage is equal to or greater than 150V, the saturationcurrent of 60 mA flows through the third switch 43, and the secondswitch 42 becomes completely the off-state.

As described above, when a current sequentially flows through a(m+1)^(th) switch according to the input voltage, a mth switch becomesthe off-state.

When the input voltage increases to reach about 200V, the fourth LEDchannel 34 begins to operate, and the current I3 and the current I4gradually flow through the third switch 43 and the fourth switch 44,respectively. Herein, a current flowing through the current sensingresistor 50 is a sum of the currents flowing through the third switch 43of 60 mA and the currents flowing through the fourth switch 44 and thefifth switch 45. Likewise, when the input voltage is equal to or greaterthan 200V, the saturation current of 80 mA flows through the fourthswitch 44, and the third switch 43 becomes completely the off-state.

Herein, when the rated voltage is 200V and the input voltage equal to orgreater than the rated voltage is inputted, an over-current, which isgreater than the current for the switch to perform the normal operation,flows through the fourth switch 44 to flow a excessive current throughthe switch, thereby generating a significant amount of heat at theswitch. When the significant amount of heat is generated at the fourthswitch 44, the switch unit 40 formed of a IC with a FET may besignificantly damaged.

Thus, in the present invention, the fifth LED channel 35 and theresistor unit 35 are connected in series to an end next to the fourthLED channel 34. When the input voltage equal to or greater than therated voltage is inputted, a current flows through the fifth LED channel35 to the resistor unit 35, and then heat generated at the switch unit40, when a voltage equal to or greater than the rated voltage inputted,is distributed to the resistor unit 35, thereby preventing thegeneration of excessive heat at the switch unit 40.

That is, according to the present invention, when the resistor unit 35is connected to the last end of the LED unit 30, the voltage isdistributed at the resistor unit 35 and a voltage equal to or greaterthan the rated voltage is inputted, the heat generated at the fourthswitch 44 is distributed to the resistor unit 35, thereby preventing thefourth switch 44 from overheating. In this way, according to the presentinvention, when the input voltage equal to or greater than the ratedvoltage is inputted, the switch unit 40 is not overheated, therebyproviding the stability of the switch unit 40 formed of the IC.

In addition, in the present invention, in order to prevent damage of theswitch unit 40 by inputting the over-current to the switch unit 40 whena voltage equal to or greater than the rated voltage, and in order toprevent damages by the heating caused by continuous inputting thevoltage equal to or greater than the rated voltage and caused bycontinuous inputting the over-current to the switch unit 40, the switchcurrent blocking unit 60, which blocks the current flowing through theswitch unit 40, is positioned outside of the switch unit 40.

The current blocking control unit 45 is positioned between the currentconversion switch 60 and the fourth switch 44. Otherwise, the currentblocking control unit 45 is positioned between the fourth switch 44 andthe current sensing resistor 50, as shown in FIG. 33.

In addition, the current blocking control unit 45 may be positioned inthe switch unit 40 or outside of the switch unit 40 between the switchunit 40 and the current sensing resistor 50.

The current blocking control unit 45 senses the current flowing throughthe fourth switch 44, compares it with the stable operation currentvalue, and controls the current conversion switch 60 when anover-current equal to or greater than the stable operation current valueflows, to connect the internal switch between the resistor unit 35 and aground voltage, thereby blocking the current, which flows through theswitch unit 40.

Herein, the stable operation current value may be set in the currentblocking control unit 45. Otherwise, the stable operation current valuemay be set an additional memory outside of the switch unit 40. Thecurrent value flowing through the current blocking control unit 45 issensed. When the current value is greater than the stable operationcurrent value, the current conversion switch 60 is controlled, therebyblocking the current, which flows through the switch unit 40.

The blockage of current of the switch unit 40, when the input voltageequal to or greater than the rated voltage is inputted and theover-current flows through the switch unit 40 will be described indetails with reference to FIG. 36.

FIG. 34 is a diagram showing a current blocking control unit positionedbetween a switch unit and a current sensing resistor, according to someembodiment of the present invention.

The current blocking control unit 45 is positioned between the switchunit 40 and the current sensing resistor 50, as shown in FIG. 34.

When the current blocking control unit 45 is positioned outside of theswitch unit 40, a stable operation current value with which the switchunit 40 is stably operated is set in the current blocking control unit45. For this purpose, the current blocking control unit 45 may furtherhave a memory.

The current blocking control unit 45 senses the current flowing throughthe fourth switch 44, compares it with the stable operation currentvalue, and controls the current conversion switch 60 when anover-current equal to or greater than the stable operation current valueflows, thereby blocking the current, which flows through the switch unit40.

An over-current usually occurs at the last switch, that is, the fourthswitch 44, but an over-current may occur at the first through the thirdswitches due to other reasons. When the current blocking control unit 45is positioned between the switch unit 40 and the current sensingresistor 50, as shown in FIG. 34, the current blocking control unit 45may sense and monitor all current value at all switches of the switchunit 40.

FIG. 35 is a diagram showing currents applied to the positions of LEDchannels according to an input voltage, according to some embodiment ofthe present invention.

As described in FIG. 33, when a voltage equal to greater than theforward voltage Vf is inputted according to the input voltage, asaturation current flows through each of the LED channels 31, 32, 33,34.

Section a in FIG. 35 is a section in which the input voltage operatingthe first LED channel 31 is inputted. Thus, in the section a, a currentI1 flows through the first LED channel 31 and the first switch 41.

Section b is a section in which the input voltage operating the secondLED channel 32 is inputted. Thus, in the section b, a current I2 flowsthrough the second LED channel 32 and the second switch 42.

Section c is a section in which the input voltage operating the thirdLED channel 33 is inputted. Thus, in the section c, a current I3 flowsthrough the third LED channel 33 and the third switch 43.

Section d is a section in which the input voltage operating the fourthLED channel 34 is inputted. Thus, in the section d, a current I4 flowsthrough the fourth LED channel 34 and the fourth switch 44.

In FIG. 35, the section a is a section in which the first switchoperates and then the first LED channel operates. The section b is asection in which the second switch operates and then the first LEDchannel and the second LED channel operate. The section c is a sectionin which the third switch operates and then the first LED channel, thesecond LED channel, and the third LED channel operate. The section d isa section in which the fourth switch operates and then the first LEDchannel, the second LED channel, the third LED channel, and the fourthLED channel operate.

FIG. 36 is a diagram showing the blockage of a current flowing through aswitch unit, when an input voltage equal to or greater than the ratedvoltage is inputted, according to some embodiment of the presentinvention.

As described above, the current blocking control unit 45 senses theover-current flowing through switch unit 40, compares it with the stableoperation current value, and then control the current conversion switch60 to blocks the current flowing through the switch unit 40 when theover-current current is greater than the stable operation current value.

This operation will described with reference to FIG. 36.

First, “V1” indicates the maximum voltage within the rated voltage. “V2”indicates the maximum voltage outside of the rated voltage. “Vx”indicates the input voltage equal to or greater than the rated voltage.“Iset” indicates the stable operation current value. Imax indicates thecurrent value flowing through the LED unit 30 when the input voltage isV2.

When the input voltage is inputted within the rated voltage, the currentflowing through the switch unit 40 changes in the sequence ofI1→I2→I3→I4→I1 to perform the operation, as shown in FIG. 35.

However, the input voltage is inputted outside of the rated voltage,that is Vx (a voltage between V1 and V2), the current flowing throughthe fourth switch 44 increases as shown in FIG. 36.

The increasing current I4 reaches the stable operation current valueIset, the current blocking control unit 45 controls the currentconversion switch 60, thereby blocking the current, which flows throughthe switch unit 40. Thus, in the switch unit 40, the current increasesduring a range, the section e subtracted by the section f, the currentdoes not flow in the switch unit 40 during the section f.

In FIG. 36, the case when the input voltage equal to or greater than therated voltage is inputted, the current flowing through the switch unit40 corresponds to the hatching area. As shown in FIG. 36, the currentdoes not flow through the switch unit 40 in the section f.

When the voltage Vx decreases and the current flowing through the LEDunit 30 decreases to be lower than Iset, the current blocking controlunit 45 controls the current conversion switch 60 to flow the currentthrough the switch unit 40.

In addition, the present invention has distinguishable featuresaccording to the power consumption.

From the first switch to the fourth switch, when the input voltageincreases, the n^(th) switch is operated by the remained voltage formedby subtracting the forward voltage at the n^(th) LED channel. When themore voltage is inputted, the n^(th) switch becomes the off-state andthe (n+1)^(th) switch operates so as to increase the power consumption(heat generation). However, the total power consumption is within aspecific system standard range.

In addition, according to the present invention, the forward voltages Vfof the LED channels are unevenly redistributed, and then the powerconsumed at each switch becomes almost same. That is, the forwardvoltage Vf of the (m+1)^(th) LED channel increases greater than theforward voltage Vf of the mth LED channel, and then the powerconsumption at the mth switch and the power consumption at the(m+1)^(th) switch become almost same. By the redistribution of theforward voltages Vf of the LED channels, the heat generation at theswitch unit 40 becomes same regardless of the change of the inputvoltage.

Herein, although the forward voltage Vf of each LED channel can befreely changed, the total amount of the forward voltages Vf is set asthe maximum value of the input voltage.

The lighting device of the present invention described above hasadvantages as follows. Since the switch current blocking unit isincluded, when a voltage equal to or greater than the rated voltage isinputted to flow an over-current through the switch unit formed of IC,the current flowing through the switch unit is blocked, therebyprotecting the switch unit. In addition, the FET switches can beautomatically switched according to the input voltage without any inputvoltage sensing circuit or any input period sensing circuit. Inaddition, since the switch unit can be simply formed, additional LEDchannels can be added in the same area. In addition, since the forwardvoltage Vf at each LED channel can be controlled and redistributed, theefficiency of the switch unit increases and the combination of LEDs canbe freely performed.

While the present invention has been particularly shown and describedwith reference to preferred embodiments thereof, it will be understoodby those skilled in the art that various changes in form and details maybe made therein without departing from the sprit and scope of theinvention as defined by the appended claims. Therefore, the scope of theinvention is defined not by the detailed description of the inventionbut by the appended claims, and all differences within the scope will beconstrued as being included in the present invention.

The invention claimed is:
 1. A light emitting diode (LED) lightingdevice, comprising: a circuit for receiving an input power from a powersource and outputting a rectified power; an LED unit comprising aplurality of LED channels connected in series, each LED channel having afront end and a rear end; a current sensing resistor; and a switchcircuit unit comprising a plurality of switches, wherein an N^(th)switch is connected to the rear end of an N^(th) LED channel so as tocontrol an operation of the N^(th) LED channel, and is controlled by asum of a current of the N^(th) switch and a current of an (N+1)^(th)switch, which flows through the current sensing resistor, wherein,forward voltages of the LED channels are unevenly redistributed so as tokeep power consumption between the N^(th) switch and the (N+1)^(th)switch substantially same, wherein the LED unit further comprises aresistor connected to a last end of the LED channels and configured todecrease heat generated at the switch circuit unit, and wherein N is apositive integer.
 2. The LED lighting device of claim 1, wherein theforward voltage of the (N+1)^(th) LED channel is greater than theforward voltage of the N^(th) LED channel.
 3. The LED lighting device ofclaim 1, wherein the LED channel comprises one or more LEDs.
 4. The LEDlighting device of claim 1, wherein a saturation current of the(N+1)^(th) switch is set to a value greater than a saturation current ofthe N^(th) switch.
 5. The LED lighting device of claim 1, wherein avoltage applied to the current sensing resistor is changed by a sum of acurrent flowing through the N^(th) switch and a current flowing throughthe (N+1)^(th) switch adjacent to the N^(th) switch, and wherein, whenan input voltage is equal to or greater than the forward voltage of the(N+1)^(th) LED channel to flow a saturation current through the(N+1)^(th) switch, the N^(th) switch is configured to turn off.
 6. TheLED lighting device of claim 1, wherein the LED unit further comprisescapacitors, each connected in parallel to each of the LED channels. 7.The LED lighting device of claim 1, further comprising a switch circuitcurrent blocking unit connected in series to the current sensingresistor for sensing and blocking a current, which flows through theswitch circuit unit.
 8. The LED lighting device of claim 7, wherein astable operational current value with which the switch circuit unitstably operates is set in the switch circuit current blocking unit, andwherein, when the current flowing through the switch circuit currentblocking unit is greater than the stable operational current value, theswitch circuit current blocking unit is configured to block the switchthrough which the current flows among the switches in the switch circuitunit to block a current flowing through the switch circuit unit.
 9. TheLED lighting device of claim 1, wherein LED units are formed as blocksand the LED lighting device has a matrix connection structure, furthercomprising a block connection unit to form a specific connectionstructure when the LED units formed as blocks are connected.
 10. The LEDlighting device of claim 9, further comprising a plurality of the LEDunits each formed as blocks which are connected in parallel.
 11. The LEDlighting device of claim 9, wherein the LED channel is formed as a blockhaving one or more LEDs.
 12. A lighting device, comprising: a firstlight emitting diode (LED) operation unit including: an LED unitincluding N LED channels and a resistor unit, the LED unit beingconfigured to receive a rectified input from rectification circuitcoupled to a power source, the N LED channels being connected to eachother in a series configuration, each LED channel including a front endand a rear end, and the resistor unit being connected to a rear end ofthe N^(th) LED channel in the series configuration; and a switch circuitunit including (N+1) switches, wherein an N^(th) switch is connected tothe rear end of the N^(th) LED channel so as to control an operation ofthe N^(th) LED channel, and is controlled by a sum of a current of theN^(th) switch and a current of an (N+1)^(th) switch, which flows througha current sensing resistor, wherein the LED unit further comprises aresistor connected to a last end of the LED channels and configured todecrease heat generated at the switch circuit unit, and wherein N is apositive integer.
 13. The lighting device of claim 12, furthercomprising a second LED operation unit coupled to the first LEDoperation unit in a series configuration, wherein the second LEDoperation unit comprises: an LED unit including K LED channels and aresistor unit, the LED unit being configured to receive a rectifiedpower from the rectification circuit, the K LED channels being connectedin a series configuration, each LED channel including a front end and arear end, and the resistor unit being connected to the rear end of theK^(th) LED channel in the series configuration; and a switch circuitunit including (K+1) switches, wherein an K^(th) switch is connected tothe rear end of a K^(th) LED channel so as to control an operation ofthe K^(th) LED channel, and is controlled by a sum of a current of theK^(th) switch and a current of a (K+1)^(th) switch, which flows througha current sensing resistor, and wherein K is a positive integer.
 14. Thelighting device of claim 12, further comprising a second LED operationunit coupled to the first LED operation unit in a parallelconfiguration, wherein the second LED operation unit comprises: an LEDunit including K LED channels and a resistor unit, the LED unit beingconfigured to receive the rectified power from the rectificationcircuit, the K LED channels being connected in a series configuration,each LED channel including a front end and a rear end, and the resistorunit being connected to the rear end of the K^(th) LED channel in theseries configuration; a switch circuit unit including (K+1) switches,wherein a K^(th) switch is connected to the rear end of a K^(th) LEDchannel so as to control an operation of the K^(th) LED channel, and iscontrolled by a sum of a current of the K^(th) switch and a current of a(K+1)^(th) switch, which flows through a current sensing resistor, andwherein K is a positive integer.
 15. The lighting device of claim 12,wherein the switches comprise field effect transistors (FETs).
 16. Thelighting device of claim 12, further comprising a plurality ofcapacitors, each capacitor being disposed between the rectificationcircuit and each LED channel and being connected to each LED channel ina parallel configuration to prevent a flicker phenomenon.
 17. Thelighting device of claim 12, wherein the 1^(st) LED channel is coupledto the rectification circuit and the N^(th) LED channel is coupled tothe resistor unit which is a last element in the series configuration ofthe LED unit.
 18. The lighting device of claim 12, wherein the currentsensing resistor comprises a variable resistor.
 19. The lighting deviceof claim 12, wherein the switches of the switch circuit unit areautomatically controlled by a voltage value applied to the currentsensing resistor in accordance with a rectified input to the LED unit,without use of any input voltage sensing circuit or any input periodsensing circuit.